The open source software is a type of software, of which the authors make public the source code. In this way they support the free study of this software, and they allow other developers to make changes and extensions to this software.
This possibility is regulated through specific licenses.
An open source license can include the copyleft. Copyleft means making a software free and impose that all the changes and extended versions of the software have to be free software.
A licence, to be open source, must:
- Allow the free redistribution (the software can be sold as a member of a set of software that comes from different sources).
- Allow the possibility to get the source code.
- Allow the possibility of changes and derived works distributed under the same licence.
- Prevent the discrimination of people or groups of people.
- Prevent limitations for the use of the software.
- Prevent limitations to other software distributed together the licenced software.