Let’s take it again to RICHARD STALLMAN, “FOUR FREEDOMS”
A program is “free software” if the program’s users have the four essential freedoms:
- The freedom to run the program as you wish, for any purpose.
- The freedom to study how the program works, and change it so it does your computing as you wish. Access to the source code is a precondition for this.
- The freedom to redistribute copies so you can help your neighbor.
- The freedom to distribute copies of your modified versions to others. 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.
If software is licensed in a way that does not provide these 4 freedoms, then it is categorized as nonfree or proprietary.