Richard Matthew “rms” Stallman, born on March 16, 1953, is a developer responsible for the GNU General Public License, a system of free software licenses designed to ensure end users can use or change software however they want. This level of freedom is championed by the Free Software Foundation, of which Stallman is a founder, former leader, and prominent proponent.
Stallman also coined the term Copyleft, a practice of copyright law with one single rule: you can change copylefted software however you like, but the changed software must be made available for others to change as well.
He is the founder and head of the GNU Project, which aims to produce software that gives users the level of freedom the GPL is made to grant.
On his personal website, Stallman posts about a wide variety of topics (often fairly far removed from his work on open-source software), from his notes on airlines to his suggestions for proper genderless pronouns.