Manic building on a ManicDigger server
ManicDigger started as a third-party client for Minecraft Classic. According to the FAQ only Windows is supported but if you have Mono, you can do the following:
Get nightly binary (.zip: warning, it is a .rar), unpack.Thanks to gustavo for the instructions!
mono GameModeFortress.exe
Must.. build.. house..
Unfortunately ManicDigger has the "most commonly used textures (grass and dirt) are ugly"-feature (just like Cube2/Sauerbraten for example).
ArdorCraft
ArdorCraft runs in Java (Ardor3d) and I got it running with its webstart file. I'm not entirely sure, but it seems that development halted four months ago.
By the way, Notch (Minecraft lead dev) just posted his first (technical) article about terrain generation. How is this open source related? Weeell.... not that much, except for the following scrap of text (from here):
Once sales start dying and a minimum time has passed, I will release the game source code as some kind of open source. I'm not very happy with the draconian nature of (L)GPL, nor do I believe the other licenses have much merit other than to boost the egos of the original authors, so I might just possibly release it all as public domain.So it's future open source, right? :D