• The freedom to run the program, for any purpose.
• The freedom to study how the program works, and modify it. (Access to the source code is a precondition for this)
• The freedom to redistribute copies.
• The freedom to improve the program, and release the improvements to the public. (Access to the source code is a precondition for this)

The GNU license is just one of a number of licenses that make up the Open Source basket; but the general premise is the granting of freedoms to what you can do with the software, as opposed to a proprietary license that grants restrictions as to what you can do with the software. You'll note that there's been no discussion of ?free? software, as in ?free of charge?. Even though the term ?Open Source? is often associated with free software there's a very distinct distinction to make between the two.

Open Source software has its roots in the Free Software Foundation formed by Richard Stallman in the mid 1980s. Stallman's philosophy was that software should be free from licencing restrictions and available to be copied and redistributed. This has become confused with the concept that the software should be free of charge. As Stallman put it:

"Free software is a matter of liberty not price. To understand the concept, you should think of ?free? as in ?free speech?, not as in ?free beer?. "^[2]

This definition also helps to distinguish software licensed under the Free Software Foundation's GNU licences from 'freeware' which is licensed software that really is free of charge.