This is librejs.info, produced by makeinfo version 6.5 from man.texi. This manual is for GNU LibreJS (version 7.17, 8 October 2018), a GNU IceCat extension to detect and block nonfree nontrivial JavaScript on webpages. Copyright (C) 2011 2012 2014 2015 Loic J. Duros Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License". INFO-DIR-SECTION GNUzilla START-INFO-DIR-ENTRY * LibreJS: (librejs). Detect nonfree nontrivial in GNU Icecat END-INFO-DIR-ENTRY  File: librejs.info, Node: Top, Next: Overview, Up: (dir) LibreJS ******* This manual is for GNU LibreJS (version 7.17, 8 October 2018). * Menu: * Overview:: General purpose and information. * Disclaimer:: Emphasize what LibreJS does and does not. * Installation:: Installing LibreJS from source. * How to Use:: How to use LibreJS in IceCat. * JavaScript Detection:: How LibreJS detects nontrivial Javascript. * Free Licenses Detection:: List of licenses detected by LibreJS. * Setting Your JavaScript Free:: Information for website owners/maintainers. * LibreJS Development Notes:: Documentation about the development of LibreJS itself. * Installation Requirements:: Requirements to build and install LibreJS. * LibreJS Internals:: How LibreJS works under the hood. * GNU Free Documentation License:: Copying and sharing this documentation.  File: librejs.info, Node: Overview, Next: Disclaimer, Prev: Top, Up: Top 1 Overview ********** GNU LibreJS --an add-on for GNU IceCat and Mozilla Firefox-- detects and blocks nonfree nontrivial JavaScript while allowing its execution on pages containing code that is either trivial and/or free. Many websites run nontrivial JavaScript on your computer. Some use it for complex tasks; many use it gratuitously for minor jobs that could be done easily with plain HTML. Sometimes this JavaScript code is malicious. Either way, the JavaScript code is often nonfree. For explanation of the issue, see "The JavaScript Trap"(). If you care about freedom in your computing, and don't wish to let all and sundry make you run nonfree programs, now you can prevent it by using LibreJS.  File: librejs.info, Node: Disclaimer, Next: Installation, Prev: Overview, Up: Top 2 Disclaimer ************ * LibreJS is not a security tool. Its goal is to detect nonfree nontrivial JavaScript, and it currently does not detect whether free or trivial code is malicious or not. Other free Mozilla extensions and add-ons may be available for this purpose. * LibreJS is always a work in progress. If you find a bug, please report it to .  File: librejs.info, Node: Installation, Next: How to Use, Prev: Disclaimer, Up: Top 3 Installation ************** You can install LibreJS directly using a generated 'librejs.xpi' file, or by building it from source. You can also download it from , but due to Mozilla's review process the download isn't always up to date.  File: librejs.info, Node: How to Use, Next: JavaScript Detection, Prev: Installation, Up: Top 4 How to Use ************ 4.1 LibreJS in action ===================== After installing the add-on, you will see the LibreJS widget in the add-on bar at the top right of the browser window. After loading a page, left-click on the widget to view the deactivated JavaScript code from the page (both on page and external) and, if applicable, the scripts that were accepted. 4.2 Script Blacklist/whitelist ============================== Scripts may be blacklisted or whitelisted through the pop-up menu box. Whitelisted scripts will always be accepted and blacklisted scripts will always get rejected. It is important to note that this feature recognizes which scripts are blacklisted and whitelisted based on hash. This means that even a slight difference in a script's code will cause it to be recognized as a separate script. Sometimes, JavaScript will be dynamically generated so that it is different every time a website is loaded. These types of scripts cannot be whitelisted or blacklisted since they cannot be recognized. LibreJS has a default whitelist of scripts that are known to be free but may not declare their license in a format that LibreJS can understand. 4.3 Complaint Feature ===================== It is very important to complain when a site has nonfree JavaScript code, especially if it won't work without that code. LibreJS makes it easy to complain by heuristically finding where to send the complaint. When nonfree/nontrivial code is detected in a page, LibreJS attempts to find a relevant contact link or email for the website you are visiting. In order to do so, it will attempt to visit a few links from the current page (for instance, a link labeled "contact" on the same domain as the current page, ...) LibreJS detects contact pages, email addresses that are likely to be owned by the maintainer of the site, Twitter and identi.ca links, and phone numbers. When you complain to the website for their nonfree nontrivial JavaScript, provide them with the link to the JavaScript Trap essay so that they can get more information on what the issue is and how they can solve it on their own site. LibreJS includes a default subject line and body for the complaint email, with a link to the JavaScript Trap essay. This can be configured in the LibreJS add-on preferences in your web browser. 4.4 Options =========== You can manage LibreJS's preferences either from the extension's entry in your browser's Add-ons Manager page ('about:addons') or by clicking the LibreJS toolbar icon and then the "Settings..." button on the top right of the popup. This will open a panel containing a whitelist/blacklist manager and a section to configure your complaints messages to site owners. "Whitelist/Blacklist" LibreJS lets you whitelist or blacklist domain names and subdomains, to bypass the regular JavaScript checks. This might be useful, for example, if you are running your own code in a local web server, or if you don't want to waste computing resources on script origins you already know you can't trust. librejs provides a lists manager UI to handle both the lists on the top of its Options panel. "Complaint email subject" Configure the default subject used in complaint emails. "Complaint email body" Configure the default body used in complaint emails.  File: librejs.info, Node: JavaScript Detection, Next: Free Licenses Detection, Prev: How to Use, Up: Top 5 JavaScript Detection ********************** LibreJS considers a very strict subset of JavaScript to be acceptable for use in non-free scripts. This is meant to maximimize compatibility with websites that haven't tried to be LibreJS compatible. We consider modification of the document non-trivial. There isn't much that javascript could do that we would consider trivial, for anything else a free software license would be required. The criterion is as follows: For each function definition: * It must call only primitives. * The number of conditionals and loops must be at most 3. * It does not declare an array more than 50 elements long. * It must not call itself For the rest of the script, outside of function definitions: * It must call only primitives and functions defined above in the page. * The number of conditionals and loops must be at most 3. "function" means anything executable that gets a name, including methods. Allowed primitives exclude: * eval() * ajax * calling methods with the square bracket notation * altering the dom * most other items found as methods of the '.window' object.  File: librejs.info, Node: Free Licenses Detection, Next: Setting Your JavaScript Free, Prev: JavaScript Detection, Up: Top 6 Free Licenses Detection ************************* The machine readable format for license declarations that LibreJS uses has changed in the most recent version. This was necessary in order to not break the asynchronous JS loading model that browsers use. Scripts are now evaluated independent of eachother and strictly as they arrive.  File: librejs.info, Node: Setting Your JavaScript Free, Next: LibreJS Development Notes, Prev: Free Licenses Detection, Up: Top 7 Setting Your JavaScript Free ****************************** The first step is releasing your JavaScript under a free license. If you are already using a free library, or you're not using any third-party libraries, it might only take a few minutes. On your website, take a look at your HTML source. You can identify distinct pieces of JavaScript that might be free and some other that are nonfree. This might be the case with an analytics tracker, social media widgets, and code that runs ads. Removing these pieces of code from your site is required to have the rest accepted as free. There are often alternatives to nonfree libraries or to third-party services: * If you have used nonfree third-party code as the base to write your own code, try to find a free alternative. * If you're using a third-party service such as an analytics service, replace it with a free alternative like Piwik. * If you can't find free JavaScript that has already been developed, write it yourself! Who knows, your own solution might be the start of a brilliant project! 7.1 License tags ================ LibreJS will allow non-trivial scripts to run as long as they use a free license. In order for the license of a script to be recognized by LibreJS, it must be declared using a machine-readable license format. This format is the same for both remote in-line scripts. "// @license [magnet link] [identifier]" [Script here] "// @license-end" "Identifier" is a name of a license from the following list and "magnet link" is that license's exact corresponding magnet link. { 'Apache-2.0':{ 'URL': 'http://www.apache.org/licenses/LICENSE-2.0', 'Magnet link': 'magnet:?xt=urn:btih:8e4f440f4c65981c5bf93c76d35135ba5064d8b7&dn=apache-2.0.txt' }, 'Artistic-2.0':{ 'URL': 'http://www.perlfoundation.org/artistic_license_2_0', 'Magnet link': 'magnet:?xt=urn:btih:54fd2283f9dbdf29466d2df1a98bf8f65cafe314&dn=artistic-2.0.txt' }, 'Boost':{ 'URL': 'http://www.boost.org/LICENSE_1_0.txt', 'Magnet link': 'magnet:?xt=urn:btih:89a97c535628232f2f3888c2b7b8ffd4c078cec0&dn=Boost-1.0.txt' }, 'BSD-3-Clause':{ 'URL': 'http://opensource.org/licenses/BSD-3-Clause', 'Magnet link': 'magnet:?xt=urn:btih:c80d50af7d3db9be66a4d0a86db0286e4fd33292&dn=bsd-3-clause.txt', }, 'CPAL-1.0':{ 'URL': 'http://opensource.org/licenses/cpal_1.0', 'Magnet link': 'magnet:?xt=urn:btih:84143bc45939fc8fa42921d619a95462c2031c5c&dn=cpal-1.0.txt' }, 'CC0-1.0':{ 'URL': 'http://creativecommons.org/publicdomain/zero/1.0/legalcode', 'Magnet link': 'magnet:?xt=urn:btih:90dc5c0be029de84e523b9b3922520e79e0e6f08&dn=cc0.txt' }, 'EPL-1.0':{ 'URL': 'http://www.eclipse.org/legal/epl-v10.html', 'Magnet link': 'magnet:?xt=urn:btih:4c6a2ad0018cd461e9b0fc44e1b340d2c1828b22&dn=epl-1.0.txt' }, 'Expat':{ 'URL': 'http://www.jclark.com/xml/copying.txt', 'Magnet link': 'magnet:?xt=urn:btih:d3d9a9a6595521f9666a5e94cc830dab83b65699&dn=expat.txt' }, 'FreeBSD':{ 'URL': 'http://www.freebsd.org/copyright/freebsd-license.html', 'Magnet link': 'magnet:?xt=urn:btih:87f119ba0b429ba17a44b4bffcab33165ebdacc0&dn=freebsd.txt' }, 'GPL-2.0':{ 'URL': 'http://www.gnu.org/licenses/gpl-2.0.html', 'Magnet link': 'magnet:?xt=urn:btih:cf05388f2679ee054f2beb29a391d25f4e673ac3&dn=gpl-2.0.txt' }, 'GPL-3.0':{ 'URL': 'http://www.gnu.org/licenses/gpl-3.0.html', 'Magnet link': 'magnet:?xt=urn:btih:1f739d935676111cfff4b4693e3816e664797050&dn=gpl-3.0.txt' }, 'LGPL-2.1':{ 'URL': 'http://www.gnu.org/licenses/lgpl-2.1.html', 'Magnet link': 'magnet:?xt=urn:btih:5de60da917303dbfad4f93fb1b985ced5a89eac2&dn=lgpl-2.1.txt' }, 'LGPL-3.0':{ 'URL': 'http://www.gnu.org/licenses/lgpl-3.0.html', 'Magnet link': 'magnet:?xt=urn:btih:0ef1b8170b3b615170ff270def6427c317705f85&dn=lgpl-3.0.txt' }, 'AGPL-3.0':{ 'URL': 'http://www.gnu.org/licenses/agpl-3.0.html', 'Magnet link': 'magnet:?xt=urn:btih:0b31508aeb0634b347b8270c7bee4d411b5d4109&dn=agpl-3.0.txt' }, 'ISC':{ 'URL': 'https://www.isc.org/downloads/software-support-policy/isc-license/', 'Magnet link': 'magnet:?xt=urn:btih:b8999bbaf509c08d127678643c515b9ab0836bae&dn=ISC.txt' }, 'MPL-2.0':{ 'URL': 'http://www.mozilla.org/MPL/2.0', 'Magnet link': 'magnet:?xt=urn:btih:3877d6d54b3accd4bc32f8a48bf32ebc0901502a&dn=mpl-2.0.txt' }, 'UPL-1.0': { 'URL': 'https://oss.oracle.com/licenses/upl/', 'Magnet link': 'magnet:?xt=urn:btih:478974f4d41c3fa84c4befba25f283527fad107d&dn=upl-1.0.txt' }, 'WTFPL': { 'URL': 'http://www.wtfpl.net/txt/copying/', 'Magnet link': 'magnet:?xt=urn:btih:723febf9f6185544f57f0660a41489c7d6b4931b&dn=wtfpl.txt' }, 'Unlicense':{ 'URL': 'http://unlicense.org/UNLICENSE', 'Magnet link': 'magnet:?xt=urn:btih:5ac446d35272cc2e4e85e4325b146d0b7ca8f50c&dn=unlicense.txt' }, 'X11':{ 'URL': 'http://www.xfree86.org/3.3.6/COPYRIGHT2.html#3', 'Magnet link': 'magnet:?xt=urn:btih:5305d91886084f776adcf57509a648432709a7c7&dn=x11.txt' }, 'Modified-BSD':{ 'URL': 'http://www.xfree86.org/current/LICENSE4.html', 'Magnet link': 'magnet:?xt=urn:btih:12f2ec9e8de2a3b0002a33d518d6010cc8ab2ae9&dn=xfree86.txt' } } 7.2 Undetected Free Licenses ============================ If you are using a free license that isn't detected by LibreJS and isn't listed in the previous section, please send a message to regarding this license, where code released under this license can be found, and where to find the license text and information. Many free licenses are listed in this page:  File: librejs.info, Node: LibreJS Development Notes, Next: Installation Requirements, Prev: Setting Your JavaScript Free, Up: Top 8 LibreJS Development Notes *************************** 8.1 Dependencies ================ LibreJS 7.17 depends on a number of Node.js-based libraries that can be installed using the 'npm' utility: $ npm install acorn-loose $ npm install jssha $ npm install browserify $ export PATH=$PATH:./node_modules/.bin 8.2 Building ============ To build the extension run: $ browserify main_background.js -o bundle.js To build the extension plus create a .xpi package run: $ ./build.sh To build the extension including the automated test suite (see TEST below) run: $ ./build.sh -t or $ ./build.sh --test Note: this 'build.sh' script relies on no new source files being created. 8.3 Debugging ============= To debug LibreJS, visit the special URL 'about:debugging'. Click on 'Enable add-on debugging' then 'Load Temporary Add-on'. Navigate to LibreJS's unpacked source directory and select 'manifest.json'. Lines 39 and 40 in 'main_background.js' assign two variables controlling the verbosity of 'dbg_print()' statements. Make sure these are set to false before building a release. 8.4 Testing =========== An automated test suite runs automatically in its own tab whenever the extension is loaded as a "Temporary add-on" from 'about:debugging'. Otherwise (if included in the xpi) it can be launched from the UI by clicking the "Automated self test..." button. 8.5 Adding new whitelisted libraries ==================================== The script index.js in './hash_script' generates the default whitelist. Run it with the following command: 'node index.js > output' Then, just copy the contents of the file "output" to the appropriate place in main_background.js. 8.6 Releasing a new version =========================== Update the version number in manifest.json. Make sure debug statements are set to false on lines 39/40 in 'main_background.js'. Then run the build script 'build.sh'.  File: librejs.info, Node: Installation Requirements, Next: LibreJS Internals, Prev: LibreJS Development Notes, Up: Top Appendix A Installation Requirements ************************************ A.1 Mozilla Browser =================== You will need one of the many flavors of the Mozilla browser to use LibreJS. It can be installed on the following: GNU IceCat, Mozilla Firefox, Trisquel Abrowser, Debian Iceweasel. LibreJS works on these browsers starting from version 60. We recommend that you use the latest version of your Mozilla browser. LibreJS has been tested on a GNU/Linux distribution, but it is compatible any operating system as long as you're using a compatible Mozilla browser.  File: librejs.info, Node: LibreJS Internals, Next: GNU Free Documentation License, Prev: Installation Requirements, Up: Top Appendix B LibreJS Internals **************************** LibreJS intercepts HTTP responses and rewrites their contents after analyzing JavaScript within them. It does not remove script nodes and attributes from the page, but instead "deactivates" them by replacing their content with a commented notice. LibreJS detects the most common cases using the HTTP response method described above, but in less common edge cases, or when running code locally, LibreJS cannot detect JavaScript during the response stage.  File: librejs.info, Node: GNU Free Documentation License, Prev: LibreJS Internals, Up: Top Appendix C GNU Free Documentation License ***************************************** Version 1.3, 3 November 2008 Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. 0. PREAMBLE The purpose of this License is to make a manual, textbook, or other functional and useful document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others. This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software. We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference. 1. APPLICABILITY AND DEFINITIONS This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you". 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The "Invariant Sections" are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none. The "Cover Texts" are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words. 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Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only. The "Title Page" means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, "Title Page" means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text. The "publisher" means any person or entity that distributes copies of the Document to the public. A section "Entitled XYZ" means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as "Acknowledgements", "Dedications", "Endorsements", or "History".) To "Preserve the Title" of such a section when you modify the Document means that it remains a section "Entitled XYZ" according to this definition. The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License. 2. VERBATIM COPYING You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3. You may also lend copies, under the same conditions stated above, and you may publicly display copies. 3. COPYING IN QUANTITY If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects. 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It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document. 4. MODIFICATIONS You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version: A. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission. B. 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Preserve the section Entitled "History", Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled "History" in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence. J. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the "History" section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission. K. 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To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles. You may add a section Entitled "Endorsements", provided it contains nothing but endorsements of your Modified Version by various parties--for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard. You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one. The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version. 5. COMBINING DOCUMENTS You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers. 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ADDENDUM: How to use this License for your documents ==================================================== To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page: Copyright (C) YEAR YOUR NAME. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled ``GNU Free Documentation License''. If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the "with...Texts." line with this: with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation. If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.  Tag Table: Node: Top825 Node: Overview1818 Node: Disclaimer2665 Node: Installation3161 Node: How to Use3539 Node: JavaScript Detection7045 Node: Free Licenses Detection8332 Node: Setting Your JavaScript Free8803 Node: LibreJS Development Notes14530 Node: Installation Requirements16612 Node: LibreJS Internals17322 Node: GNU Free Documentation License17972  End Tag Table