The Free Software Foundation (FSF) is the nonprofit organization Richard Stallman established in October 1985 to support the GNU Project and the broader cause of software freedom. Its own about page describes it as “a nonprofit with a worldwide mission to promote computer user freedom” that defends “the rights of all software users.”
The FSF treats free software as a matter of liberty, not cost. By its own account it works “by securing user freedom by advancing free software development and usage,” sponsoring “the GNU Project, the ongoing effort to provide a complete operating system licensed as free software.”
A central part of the FSF’s role is legal stewardship. The organization publishes the GNU General Public License (GPL), which it calls “the world’s most popular free software license, and the only license written with the express purpose of promoting and preserving software freedom.” It also holds copyrights on much GNU software to defend it against being turned proprietary and runs a licensing and compliance effort to enforce those terms.
The Foundation grew directly out of the work begun in the GNU Manifesto, where Stallman asked for support in building a free operating system. The FSF became the institution that could employ developers, accept donations as a tax-exempt charity, and hold the project together over the long term.