Well i'd say that you can use the Torque Game Engine, but Garage Games has updated that to Torque 3D which the engine itself has had many major changes to it since this old and long outdated version that Blockland uses, i think the only way you can get the Torque Game Engine with terrains and interiors if you can find the old demo that shows off the engine's features
You can find a download to the older Blockland versions that have terrains and interiors, but the base scripts and such for the game and the engine itself are encrypted and are thus unable to be edited by those who lack the source files (a.k.a. everyone except Badspot, most likely)
Also, i believe everyone's said that it's possible that Blockland could have both terrains, interiors and shaders, but that requires re-coding the engine to make them more compatible with each other, but it's more trouble than it's worth (correct me if i'm wrong)
