I've added a beta branch to the game, which enables Linux achievements and also has the DLC contents for the upcoming release on Steam (DLC is already available on my site).
If anyone wants to test just to be sure, it would be welcome. Tomorrow the beta branch will become the default one in occasion of DLC "Bad Blood" launch.
For more info about the DLC check here:
http://www.winterwolves.com/SOTWbadblood.htm