The four software freedoms as defined by the Free Software Foundation
– 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.