VoxelSim is OpenSim (an OpenSource BSD-licensed Second Life simulator) heavily modified to use voxels instead of a heightmap terrain.
mono / .NET 3.5 nant
Compile and run from bin.
BSD
OpenSim contributors
Rob "N3X15, Fred Rookstown" Nelson
Rob Nelson (nexisentertainment@gmail.com)
You can download this project in either zip or tar formats.
You can also clone the project with Git by running:
$ git clone git://github.com/N3X15/VoxelSim