Free Software

The Free Software Foundation http://www.fsf.org/ or http://www.gnu.org/

Founded by Richard Stallman.

https://en.wikipedia.org/wiki/The_Free_Software_Definition

FourFreedoms:

• The freedom to run the program as you wish, for any purpose (freedom 0).
• The freedom to study how the program works, and change it so it does your computing as you wish (freedom 1). Access to the source code is a precondition for this.
• The freedom to redistribute copies so you can help your neighbor (freedom 2).
• The freedom to distribute copies of your modified versions to others (freedom 3). By doing this you can give the whole community a chance to benefit from your changes. Access to the source code is a precondition for this.