The GNU General Public License is a free software license by the free software foundation. It is very popular in the free and open source software community.
- The freedom to run the program for any purpose.
- The freedom to study how the program works and adapt it to your needs.
- The freedom to redistribute copies so you can help your neighbor.
- The freedom to improve the program and release your improvements to the public, so that the whole community benefits.
- Every copy of the program must be accompanied by the license text.
- Every copy of the program hast to be distributed with the human readable sourcecode.
- Every modification or derived work based on the program must be licensed under the GNU GPL, too.
- see Copyleft principle