Here are the many ways you can contact the team. Usually they will answer quite quickly, but if they don’t please be patient and give them the benefit of the doubt. Yes, that means stick around IRC longer than 2 minutes.
This mailing list is for everything development related. Feel free to chime in!
We also have a forum where you can discuss the game, ask questions and submit your creations or contributions.
Most development related discussions that need to happen in real time happen on IRC. You can find us on freenode (server: chat.freenode.net) in the #supertux channel. Please note that people might not be available all day, so wait before you leave.
We’re @SuperTux on GitHub. This is the place where SuperTux’s source code and issue tracker is hosted.
A great guide for the SuperTux 0.3 editor, created by Devyn Collier Johnson can be found at DCJTech Gaming.