The Free Software Movement began in 1983 when Richard Stallman announced the GNU project. The goal of the movement is to give freedom to computer users by replacing software which has restrictive licensing terms with free software (free as in freedom).

Most members of the free software movement believe that all software should come with the freedoms listed in the free software definition. Many hold that it is immoral to prohibit or prevent people from exercising these freedoms and that these freedoms are required to create a decent society where software users can help each other, and to have control over their use of a computer.

On the other hand, many who prefer the term "free software" and consider themselves part of the movement do not believe proprietary software to be strictly immoral. They argue, however, that freedom is valuable (both socially and pragmatically) as a property of software in its own right, separate from technical quality in a narrow sense. Moreover, they may use the term "free software" to distance themselves from claims that "open-source" software is always technically superior to proprietary software (which is often demonstrably false, at least in the short term). In this sense, they object that "open-source" advocates, by concentrating solely on technical merits, encourage users to sacrifice their freedom (and the long-term benefits thereof) for short-term conveniences that proprietary software may provide.

Supporters of Open Source argue for the pragmatic virtues of free software (aka "open source software") rather than questions of morality. Their basic disagreement with the Free Software Foundation is its blanket condemnation of proprietary software. There are many programmers who enjoy supporting and using free software but make their livings developing proprietary software, and do not consider their actions immoral. The "official" free-software and open-source definitions are slightly different, with the free-software definition generally considered to be more strict, but the open source licenses which are not considered to be free software licenses are generally obscure, so in practice virtually all open source software is also free software.

The main legal difference between the 'free software' license (GNU Public License or GPL) and other open source licenses is in the status of derived works. Software that is based on GPL'd code or distributed with GPL'd code included in the main body of the software must also be licensed under the GPL. Under some of the other licenses, like the Jabber license, open source code can be used unaltered in proprietary implementations and in some cases, such as the Artistic License that governs Perl, any substantially altered verion of the code can be copyrighted. All open source licenses including the GPL guarantee anyone the right to commercialise implementations of the code. The idea that GPL imposes limitations on commercial use is a common misconception.

Many members of the Free Software Movement believe that also other materials currently subject to copyright and patent law should be freed. Some believe that some classes of works should not be freely modifiable, e.g. opinion pieces in order to prevent misrepresentation of the author's beliefs, fictional works, or licenses themselves.

See also: free software license, open source license, GNU Manifesto, Open source, Free Software Foundation, Hacker community

ja:フリーソフトウェア運動 zh:自由软件运动