Copyleft

Copyleft refers to a license that allows free re-use and modification of creative work so long as any works derived from the original remain available on the same terms.

Copyleft, formally known as the “General Public License” or GPL, was initiated by computer programmer Richard Stallman and the Free Software Foundation. By protecting the creativity and energy of the commons from private appropriation, the GPL has enabled communities of programmers to build shared bodies of code, such as free software and opensource software. A similar set of licenses for other types of creative works has been devised by the Creative Commons.