Richard Stallman's Free Software Definition, adopted by the Free Software Foundation (FSF), defines free software as a matter of liberty not price, and it upholds the Four Essential Freedoms. The earliest-known publication of the definition of his free-software idea was in the February 1986 edition of the FSF's now-discontinued GNU's Bulletin publication. The canonical source for the document is in the philosophy section of the GNU Project website. As of August 2017, it is published in 40 languages.

1.2. Open source

2. History

Example of link

3. Usage

3.1. FOSS benefits over proprietary software
3.2. Drawbacks compared to proprietary software
3.3. Adoption by governments
3.4. Adoption by supranational unions and international organizations

4. Production

5. Issues and incidents

5.1. GPLv3 controversy
5.2. Skewed prioritization, ineffectiveness and egoism of developers
5.3. Commercial ownership of open-source software
5.4. Legal cases