paralipsis: Unless there's an announcement forthcoming, it looks like they've quietly added the Mac and Linux versions of The Long Dark with very little fanfare. I've seen notifications appear in my library of the changes, but no forum or news post about it.
There's a bit of a lag on the store page too. It lists the Mac version, which was added a couple of days ago, but does not yet mention the Linux version. There is now a link to all three installers in my library though if anyone was hanging out their release.
Both Linux and Mac versions are up now and the gamecards were updated. Enjoy! Good job Hinterland Studio! :)