I'm one of the developers for 0AD, and I have to say it's really not that hard to get started. I began checking out the source code and developing patches only about eight months ago (I didn't know /any/ C++ when I started, only some JS and Python), and in the mean time I'm gotten very familiar with the codebase and joined the official team. In fact, the multiplayer lobby in this release was primarily developed by myself.

Feel free to join us on #0ad or #0ad-dev on quakenet if you have any questions.