As was stated during the kickstarter, Mac and Linux development was stopped due to lack of resources, and only restarted, and those versions confirmed, once the goal was reached.
The Kickstarter page is still listing Linux as supported operating system. Coming to: Windows, Linux, Mac. On Apr 25 2014 tha status was: "Furthermore, you can expect a Mac version on Steam Early Access and a version of the game for Linux some time after its full release on PC/Mac"
