Now, this isn’t exactly groundbreaking stuff, but it does really demonstrate the fact that all tablets (especially the more recent and hackable ones) are just small computers. Anything’s possible — convenient, perhaps not, but if you’re looking to take full advantage of the hardware you’ve just bought, there are definitely ways to go about doing that.
In this case, you’ve got Ubuntu running in a virtual machine, and the Minecraft server software running inside it. I know, it’s kind of cheating, but that’s the point, isn’t it? You can cheat.
Tracking the world is a bit buggy (player tracking also, I’m guessing), perhaps due to the caching of the worldstate in the VM and serving up outdated block data, but that’s, you know, just an engineering problem. It’d be nice to be able to carry around a little Minecraft world with you, especially if you could set it up in an ad-hoc network with a few friends at a park. Wait, why wouldn’t you just throw a frisbee around or something?