An Acronym for GeneralPublicLicense.
The General Public License (GPL) is published by the Free Software Foundation and is intended to guarantee every user the freedom to run, study, adapt, improve, and redistribute the software that it covers.
Version 1 was released in 1989, version 2 in 1991 and version 3 in 2007. http://www.gnu.org/licenses/gpl.html
52 pages link to GPL: