Free software movement
The free software movement advocates the creation and sharing of free software (compare open source).
- Run the program for any purpose
- Study how the software works and modify it to meet your needs
- Distribute copies of the software
- Publish modifications to the software
In order to fulfill these requirements access to the source code is essential, so free software is a type of open source software. The right to distribute the software may be subject to a clause that ensures that future recipients of the software have the same freedoms.
Free software and Open Source software
- The two terms describe almost the same category of software, but they stand for views based on fundamentally different values. Open source is a development methodology; free software is a social movement. For the free software movement, free software is an ethical imperative, because only free software respects the users' freedom. By contrast, the philosophy of open source considers issues in terms of how to make software “better”—in a practical sense only. 
Articles by Richard Stallman: