The Castle Doctrine, a massively-multiplayer game developed and published by Jason Rohrer, has just arrived on Steam for Linux.
There aren't many massively-multiplayer games on the Linux platform, and I can tell you for a fact that this is the first MMO game of burglary and home defense.
“It's 1991, and things are bad. You're a guy with a house and family. Other players are coming to take what's yours. Build security to stop them. Study their houses, buy tools, and break in to take what's theirs. Everything you do is permanent,” reads the official synopsis.
The Linux hardware requirements are also quite low: a 900 MHz processor, 40 MB RAM, Onboard Graphics, Broadband Internet connection, 10 MB available space.
The binary for this game was built on Ubuntu 12.04, but it should work fine on other distributions.
Check the official announcement for more details about this release.