Richard Matthew Stallman is the programmer who set the free software movement in motion. On September 27, 1983, he posted a message to Usenet announcing, in his own words, “Starting this Thanksgiving I am going to write a complete Unix-compatible software system called GNU (for Gnu’s Not Unix), and give it away free to everyone who can use it.” That announcement, preserved on gnu.org, marked the public start of the GNU Project.
In 1985 Stallman wrote the GNU Manifesto to ask for support in building the system. There he laid out the principle that would define his work: “Everyone will be permitted to modify and redistribute GNU, but no distributor will be allowed to restrict its further redistribution.” He framed software sharing as a matter of liberty rather than price, distinguishing his aims from the cost-focused arguments others would later make.
Stallman did not only write essays; he wrote foundational software. He created GNU Emacs, described on its project page as “an extensible, customizable, free/libre text editor,” whose core is an interpreter for the Emacs Lisp programming language. He also wrote the GNU Compiler Collection (GCC), and he devised the copyleft licensing technique embodied in the GNU General Public License.
To carry this work forward, Stallman founded the Free Software Foundation, which sponsors the GNU Project and publishes the GNU GPL. Through his writing and his code, he established the four freedoms (to run, study, share, and modify software) that remain the test of whether a program is free.