Copyleft is a licensing concept that allows creators to share their work while ensuring that any derivative works remain free and open. This means that anyone can use, modify, and distribute the original work, as long as they also share their modifications under the same terms. This approach promotes collaboration and innovation, encouraging a community-driven development model. The most well-known example of copyleft is the GNU General Public License (GPL), which was created by Richard Stallman in the 1980s. Copyleft is often associated with the Free Software Foundation and the broader open-source movement, which advocates for software that is freely accessible and modifiable by anyone.