Ubuntu is made up of a collection of free and open-source software. This page discusses what free and open-source actually means, and attempts to explain your rights with respect to free software.
Note: Do not use this page as a source of legal advice. It is only intended as a guide, and the correctness of information here cannot be guaranteed.
What is a Free License?
A free license is one which generally grants an individual the legal right to use, copy and distribute material (such as software) without restriction.
According to the Open Source Initiative, free software licenses have the following features:
- Allow you to distribute or sell the software yourself
- Make the source code of the software available
- Allow you to make modifications and to produce derived works
- Do not allow discrimination against any group of people or people carrying out a specific type of work
- Do not restrict the use of other software
Open source refers to making the source code of a computer program available to be viewed and possibly modified. It also refers to a way of producing software which is open source; open source software projects often share similar ways of doing things, such as reporting problems with the software.
Free has a couple of different meanings in the English language, but when referring to a free license it means free as in speech (unrestricted). Very often, free software is also free as in beer (no cost), although it doesn't necessarily have to be.
Source code is the actual programming code which makes up a computer program. To use a computer program you must normally compile source code, which turns the program into a form which computers can use but humans can't. If the source code is made available however, people can read and change the code to alter/improve how the program works.
Proprietary software is software which doesn't have a free license and for which there is no open access to its source code.
Dual licensing is where software or some other work is distributed under a choice of two licenses. For example, MySQL is distributed under either a free license (which means that you have to release any changes you make to MySQL to the public) or a commercial license (which allows you to make modifications but doesn't force you to release them to the public).
Copyleft is a type of license which requires that any changes you make to the software must be released to the general public under a free license. This encourages people to share their work and helps to improve the software.
The Free Software Foundation is responsible for two of the most popular licenses, the GPL and the LGPL, along with other licenses for documentation and the like. Most of the software in Ubuntu is distributed under the GPL or LGPL.
The MIT license is non-copyleft, which means that software can be used in proprietary software.
Creative Commons Licenses
Creative Commons licenses offer a way for authors to distribute their works freely, while preserving certain rights. Creative Commons licenses are normally used on material such as photos, books/articles and music.
There are many other free licenses in common use, but most are similar to one of those listed above. See the pages below for listings of popular free licenses: