This and Jason Rohrer's other games are all in the public domain and have source code available. The code is mostly on GitHub these days, but some of it may not have moved yet. His recent games have all be multiplayer of some variety, but personally I liked Cultivation (gardening community) and Primrose (puzzle) the most.

http://hcsoftware.sourceforge.net/jason-rohrer/ https://github.com/jasonrohrer https://sourceforge.net/projects/hcsoftware/ https://sourceforge.net/projects/minorGems/