Contributing to BIRD

Hello everybody, my name is Jan, I am a backend developer. I'd like to get to know BIRD's codebase. My main motivation is to improve my C language skills. I used BIRD some time ago and am interested in networking. I started reading the Coder's Doc 2.0. Do you accept contributions from people outside of CZ.NIC? If you do, what one can do to contribute? Any tasks suitable for newcommers? Cheers Jan