Manic Digger is an open-source implementation of block-building games as made famous by Minecraft. Manic Digger aims to be a generic platform ontop of which you can create your own game-types and scenerios. Through server-side scripting, any type of block-building game should be possible.

disulfiram says

1/10 - Agree (4) Disagree (8)

Too imperfect. Maybe with time it will get better, but for now that's all I can give it.