Free games consist of free software and free media.
Free software is software that respects users' freedom and community. "Free" in this case does not mean gratis, and free software is not necessarily freeware. To understand the concept, think "free speech" not "free beer".
Free media are all kinds of media (images, videos, sound effects) that may be modified and shared similarly to free software. See free media license for details.
Definitions and important differences
There are three major maintainers of freeness definitions and license lists:
- Free Software Foundation (FSF)
- Open Source Initiative (OSI)
- Debian, maintaining Debian Free Software Guidelines (DFSG)
The criteria of acceptance are different. For example,
- Free Software Foundation does not require free software to contain only free media, while Libregamewiki does.
- Debian requires everything in its “main” repository to be free, including media.
- Debian and OSI approved Artistic License 1.0, but FSF did not.
Free Software Foundation
Software is free software if it has the four freedoms layed out in The Free Software Definition:
- Freedom 0: The freedom to run the program, for any purpose.
- Freedom 1: The freedom to study how the program works, and adapt it to your needs.
- Freedom 2: The freedom to redistribute copies so you can help your neighbor.
- Freedom 3: The freedom to improve the program, and release your improvements to the public, so that the whole community benefits.
Although it is not specified in those four lines, that includes for-profit performance of those activities; also, copyleft is allowed.
For the practical application of the definition, see FSF’s page Various Licenses and Comments about Them