I've picked this game up. Currently there are some issues with it for linux. They are actively being resolved.
If you opt into the beta you can get a version that should work on a 32 bit install of Ubuntu 12.04. It didn't work out of the box for me on any 64 bit platforms I've tried.
It is currently under active development and I expect it will be ready for us soon :)
[–] Alzarath [S] 0 points 1 point 1 point (+1|-0) ago
Now that I think about it that title might be a little misleading. The game is still considered in Early Access, just that it's officially available for Linux. Sorry for any potential confusion.
The game is currently 25% off on Steam until June 22, 2015. Keep in mind the price for the game will be lower after it's released from Early Access.