Open Source
Previously refered as "Free Software", Open Source means that the users of the software have to be freely allowed (without having to pay, or ask for permission to use):
- to use the software
- to study how the software works, to improve it, publish these modifications (free access to the source code is then required)
- to distribute copies, freely or not
Contribution to the code source is therefore possible to whom may wish so, no matter where one comes from. Most of the time, developpers participate to the improvement of software voluntarily.
The concept of Open Source is explained in details by the "Free Software Fundation" (FSF) who created it.