GPL

The GNU General Public Licenses are a series of widely used free software licenses. The GPL is a copyleft license, which means that it guarantees end users the freedom to run, study, share, or modify the software, but requires them to publish all derivative works and modifications under the same or equivalent license terms. The GPL was the first copyleft license available for general use. It was originally written by Richard Stallman, the founder of the Free Software Foundation (FSF), for the GNU Project. The license grants the recipients of a computer program the rights of the Free Software Definition. The GPL states more obligations on redistribution than the GNU Lesser General Public License and differs significantly from widely used permissive software licenses such as BSD, MIT, and Apache. Read more on Wikipedia