There's a distinction between "free software" and "open source" though very similar.
In 1983, the GNU (GNU's Not Unix) was formed to create a free Unix-like operating system... "Free" refering to freedom and not price.
These freedom are: (0) The freedom to run the program, for any purpose; (1) The freedom to study how the program works and adapt it to your needs. Access to the source code is a precondition to this; (2) The freedom to redistribute copies so you can help your neighbor. (3) The freedom to improve the program, and release your improvements to the public, so that the whole community benifits. Access to the source code is a precondition to this....
Open Source is a seperate group from which the FSF (where the GNU project came out of) started. In 1998, some of the people in the free software community began using the term Open Source to describe what they do. The Open Source term became quickly associated with a diffrent approach. A diffrent philosophy, diffrent values, and even diffrent criterion for which licenses are acceptable...
I like the idea of "free" software; but I eventually want to make money off the video games I program.... I decided to use the Open Source model for practical reasons... Though I support what GNU does, and I do use a lot of "free" and "open source" products; I have nothing against propitery software... I feel more comfertable with the help of the the internet in the development of the video games... It's cost effective; and it works.
The Free Software Definition
Why Free Software is better than Open Source