Extensions and GPL
From Joomla! Documentation
""GPL" stands for "General Public License". The most widespread such license is the GNU General Public License:, or GNU GPL for short. This can be further shortened to "GPL", when it is understood that the GNU GPL is the one intended."
About Joomla! and the GPL
The Joomla Project is a GPL community, which means not just that a particular Free and Open Source license is used for Joomla software, but also that we believe in the mission and values behind that license. These include collaboration, community, and freedom. The GPL license embodies these values.
- What GPL version is Joomla! licensed under? Joomla! is licensed under GPL version 2 or later.
The Joomla Extensions Directory and the GPL
The Joomla Extensions Directory (JED) is important for many reasons: it makes it easier for users to find extensions, and it helps support the development of a vibrant and healthy commercial and non-commercial development community around Joomla. However, it may also be unintentionally undermining our support of the GPL by including extensions and other applications that run counter to it. JED its oriented by overall mission of the Joomla Project. The Joomla! Project has determined that the Joomla! Extensions Directory (JED) should be a community resource that fully embodies the project's values, especially freedom as embodied by the GPL license.
- Since March 31 2009 the Joomla! Extensions Directory (JED) no longer accept non GPL and since July 1 2009 only GPL extensions are allowed to be listed here .
- These changes were designed to strengthen the project's commitment to its core mission, vision and values as articulated in September 2008.
GPL license required
Extensions must be licensed as GPL in order to be listed Additional restrictions may not be placed on top of the GPL.
- Do note that the GPL does allow developers to charge for their products See: Free and Commercial extensions
Extensions pack - general requirements
JED needs to be able to monitor files and make it easier for users to understand the terms under which they purchase/download extensions. This is why, to be listed at JED, you need to comply with additional terms that will improve directory maintenance and trust form directory users.
- Publish under a GPL license - See: Versions of the license
- Include GPL notices on XML and PHP files - See: Examples and how-to.
- Provide a copy of the GPL license within your package:
- this file doesn't need to be installed with the extension, just included with the package as a text file
- There is a text available to copy and save has text file: 
- Copyright notice in all files as required by GPL license.
- Encrypted or encoded extensions, whether or not they are GPL licensed, will also be excluded.
We support the original project developer whenever possible to maintain the integrity of the listings and also support developers who are building and innovating on the Joomla platform.
Forked project must represent a significant code improvement, either in features or security and structure.
- See requirements to be listed at JED: Forked Extensions
- Who will you intend to support developers The Joomla team is strongly committed to supporting both commercial and non-commercial Joomla developers. We have implemented some policy changes to enhance our support for developers. Therefore we will not link to collections of GPL extensions that are not submitted by the original developer.
- Does this mean there will be no more commercial extensions in the JED? No! Commercial extensions with the GNU GPL license and that are not encrypted are welcomed and encouraged in the JED.
- Who will be able to submit extensions? Only the original developer! We think that the best place to get an extension is from the original developer of that extension.
- What if I think my extension doesn't violate the Joomla! license? This is a policy in favor of software freedom and the mission, vision and values of the Joomla! Project, not one about technical issues in licensing.
- Can I use a GPL compatible license? No! The JED will only list extensions licensed using the GNU GPL. The only license that truly embodies the spirit of the GPL is the GPL.
- Can I use libraries in my GPL extension that are GPL compatible? Yes!
To know more about licensing your software:
- Free Software Foundation | How to use GNU licenses for your own software
- Open Source Matters: Joomla! License FAQ
- Open Source Matters: Licensing your extension
Before submitting an extension to JED, please read:
- GNU GPL Licenses: http://www.gnu.org/licenses/licenses.html
- What does "GPL" stand for? http://www.gnu.org/licenses/gpl-faq.html#WhatDoesGPLStandFor
- JED to be GPL Only by July 2009 http://community.joomla.org/blogs/leadership/636-jed-to-be-gpl-only-by-july-2009.html
- Joomla project's mission, vision and values. http://opensourcematters.org/policies/104-mission-vision-and-values.html
- GPLv3 http://www.gnu.org/licenses/gpl-3.0.txt
- Why does the GPL require including a copy of the GPL with every copy of the program? http://www.gnu.org/licenses/gpl-faq.html#WhyMustIInclude