https://git.io/open.mp
This is the direct (nice) link to our github organisation, on which most development will be hosted. There is one notable absence for now - the actual mod. However, all graphics, operations, and modes are being put on there.
Interested in graphics? Star the graphics repo and make some issues.
Want to improve the forums? They're there as well.
Got a simple mode you want including with the server? We'd love to see it.
Note that everything will be MPL 2.0 or CC-BY-SA 3.0. We are setting up CLAs, which is basically just a way of enabling you to say you agree to let us use the things you submit.