The term "open source" refers to something people can modify and share because its design is publicly accessible.
The term originated in the context of software development to designate a specific approach to creating computer programs. Today, however, "open source" designates a broader set of values—what we call "the open source way." Open source projects, products, or initiatives embrace and celebrate principles of open exchange, collaborative participation, rapid prototyping, transparency, meritocracy, and community-oriented development.
What is open source software?
Open source software is software with source code that anyone can inspect, modify, and enhance.
"Source code" is the part of software that most computer users don't ever see; it's the code computer programmers can manipulate to change how a piece of software—a "program" or "application"—works. Programmers who have access to a computer program's source code can improve that program by adding features to it or fixing parts that don't always work correctly.
What's the difference between open source software and other types of software?
Some software has source code that only the person, team, or organization who created it—and maintains exclusive control over it—can modify. People call this kind of software "proprietary" or "closed source" software.
Only the original authors of proprietary software can legally copy, inspect, and alter that software. And in order to use proprietary software, computer users must agree (usually by signing a license displayed the first time they run this software) that they will not do anything with the software that the software's authors have not expressly permitted. Microsoft Office and Adobe Photoshop are examples of proprietary software.
Open source software is different. Its authors make its source code available to others who would like to view that code, copy it, learn from it, alter it, or share it. LibreOffice and the GNU Image Manipulation Program are examples of open source software.
As they do with proprietary software, users must accept the terms of a license when they use open source software—but the legal terms of open source licenses differ dramatically from those of proprietary licenses.
Open source licenses affect the way people can use, study, modify, and distribute software. In general, open source licenses grant computer users permission to use open source software for any purpose they wish. Some open source licenses—what some people call "copyleft" licenses—stipulate that anyone who releases a modified open source program must also release the source code for that program alongside it. Moreover, some open source licenses stipulate that anyone who alters and shares a program with others must also share that program's source code without charging a licensing fee for it.
By design, open source software licenses promote collaboration and sharing because they permit other people to make modifications to source code and incorporate those changes into their own projects. They encourage computer programmers to access, view, and modify open source software whenever they like, as long as they let others do the same when they share their work.
Frequently Asked Questions
What license does Joomla! use?
The GNU General Public License. http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
Within the context of this FAQ, "GNU GPL" and "GPL" refer to the GNU General Public License.
What is the difference between the GPL and the LGPL?
The GNU GPL is intended to be used for applications whereas the GNU LGPL is intended to be used for application libraries. The Joomla! Content Management System is an entire application that utilizes a multitude of libraries, both GPL and LGPL, and thus is licensed under the GPL license.
Where can I read more about the license?
The GNU General Public License: http://www.gnu.org/licenses/gpl.html
The GNU GPL Frequently Asked Questions (FAQ): http://www.gnu.org/licenses/gpl-faq.html
The philosophy behind the GNU: http://www.gnu.org/philosophy/
What is the definition of Open Source/Free Software?
We want all parties to come into compliance with our license, as it strengthens our ability to defend and protect Joomla! We do not have the will nor the means to go after everyone who violates our license nor do we intend to. We are asking the community to voluntarily comply with the GPL.
What is the difference between "commercial" and "proprietary"?
Commercial software means that there is some sort of commercial activity surrounding that software. It could be a business that develops it and charges money for distribution, support, documentation, customization, etc. Commercial software is not necessarily proprietary software and proprietary software is not necessarily commercial software. Proprietary software means that you do not have the right to copy, modify, and redistribute that software.
Does the license allow someone to sell a copy of Joomla!?
Yes. The Preamble of the GNU GPL states "when we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things."
Also see: http://www.gnu.org/licenses/gpl-faq.html#DoesTheGPLAllowMoney
Can I remove the Joomla! Copyright notice in the footer region (and other related questions)?
Yes, you can remove the Joomla! copyright notices from any part of the output that the Joomla! application generates. You may not remove the copyright notice from the source code itself.
Can I remove the Joomla! Copyright notice in the Meta information of a Joomla! website?
Yes, you can remove the copyright notices from any part of the output that the Joomla! application generates. You may not remove the copyright notice from the source code itself.
What should I do if I find a possible violation of the GPL?