Cube Universe is a voxel game similar to Minecraft, but on different planets and in space.

I found a way to crack this game and uploaded it here. In order to play it, you need to block traffic to login.beosar.com, for example by adding a rule in your hosts file or simply disconnecting from the Internet, so you can play in offline mode. The credentials you enter don't seem to matter. I don't think there is a way to get updates for the game without registering and buying the game though