Free software foundation (FSF)

The Free Software Foundation is best known for its sponsorship of the GNU project. GNU is a recursive acronym which stands for "GNU'S Not Unix". The GNU Project was founded in 1984 to develop a complete free Unix-compatible operating system, to be called GNU. "Complete" means covering the full range of components of Unix--kernel (q.v.), libraries, shells, editors, compilers, development tools, mailer, and the rest. "Free," here, means that users have certain freedoms, including the freedom to use the system for any purpose, and to redistribute copies, either verbatim or modified, either gratis or for a fee. As a practical matter, the freedom to modify entails availability of source code.