If you're interested in contributing to RabbitVCS, we would appreciate your help! If you're not sure what level you're at, or what you can do, the best thing is to have a look through the open issues and pick one that you'd feel comfortable tackling.
If you are more at the level of tinkering with the core of things, then once you've wrapped your head around the code you might see areas that need work (or look at the roadmap and known issues). You can also get in touch with us to find out what our current focus might be.
Either way, contact the developers, post to the devel mailing list or ask on IRC (#rabbitvcs on chat.freenode.net) if you have any questions or patches to contribute. There aren't any hoops to jump through for commit access or anything like that, but it's good for us to know where things are coming from first.
Any contributions should be compatible with the GPLv2 or later.
Maintaining RabbitVCS's code is easier when it all conforms to a single style guide. Please follow our guide for all patches.
It's not required but it's a good idea to take a look at the the development installation instructions, these should make it easy to switch between branches and whatnot without fiddling too much. Decide for yourself if the instructions are overkill for what you want to do.