Yes, its Open source. The tools we use (Perl, PostsgreSQL, Apache ++) is also Open source. Open source means that the source code of the software is available for free to everyone and you can modify the code and distribute it yourself. http://en.wikipedia.org/wiki/Open_source
Look for a place to contribute. This means not only programming, but also documentation, theme design, art work, or architectural design. Join the mailing list.