From the dev's blog:
No more Linux and Mac support!
Unfortunately, we will no longer support Mac and Linux. Since we are three people, and we do not work on Linux or Mac, we don't have the time or resources to develop to these platforms. As the game becomes more complex, more and more problems arise specifically on Mac and Linux, which means we would have to spend too much time fixing those problems. We're really sorry about this, and we hope to be able to port to these platforms in the future! We hope you understand!
I'm on Linux myself, so I sympathize. But it looks like we shouldn't hold our collective breaths.