Short for GNU General Public License, the GPL is a general license published by GNU (GNU's Not Unix) project. Any software author may use the GPL to legally control the way their software may be used by others. It is a copyleft license, meaning that any code derived from GPL-licensed code must also be licensed under the GPL.
Anyone who uses GPL-licensed software, and abides by the license terms, is guaranteed four fundamental freedoms as defined by the Free Software Foundation:
- The freedom to run the program as you want, for any purpose.
- The freedom to study how the program works, and change it so it does your computing as you want.
- The freedom to redistribute copies so you may help your neighbor.
- The freedom to distribute copies of your modified versions to others.