CodeCombat is a multiplayer programming game for learning how to code. See the Archmage developer wiki for all information.
We just open-sourced everything on 2014-01-03 as a preview release for our Archmages who have been waiting to contribute. We will announce it fully on Monday. Please poke around, add issues, work on issues, and have fun! We'd love to see as many contributors as possible this weekend, so no contribution is too small.