Though there is evidence of use of the term copyleft as far back as the mid seventies, the real pioneer of the principle is US software developer Richard Stallman. Having in 1983 launched the GNU project, a mass collaboration for the development of free software, Stallman went on to author the GNU General Public License, the first copyleft license to fall into general use. This license ensured that maximal rights were continually transferred to all users of the software, regardless of any subsequent revisions anyone made to the original program.