Free software license

1. The freedom to run the program for any purpose
2. The freedom to study and modify the program
3. The freedom to copy the program
4. The freedom to redistribute modified versions of the program

A license which preserves those freedoms for modified works is a copyleft license. See Free software movement for more information.

The Free Software Foundation maintains a list of free software licenses at their web site. The list distinguishes between free software licenses that are compatible or incompatible with the FSF license of choice, the GNU General Public License, which is a copyleft license. The list also contains licenses which the FSF considers non-free for various reasons. The list, which differs slightly from the open source license list, can be found at http://www.gnu.org/philosophy/license-list

See also:

• Free software
• Free Software Foundation
• Open source license