If you have the Mono Framework installed, the good news is that Another Star is fully playable in Linux (and should be on a Mac as well, but I currently have no way of testing it). The bad news is that you might have to jump through an extra hoop to make it work.
When a program looks for files, it does so in relation to what’s called the “current directory”. In Windows, this is whatever folder the program’s executable file was launched from. But in Linux, it’s usually the home directory. Unfortunately, the “leaked” build of Another Star does not take this into account which will cause the game to fail.
To get around this, the easiest thing to do is copy Another Star’s “Data” folder to the home directory. You can delete it whenever you’re done with it without affecting your saved games, since those will always be in your documents folder no matter the platform. Alternatively, you can change the current directory, but that’s beyond the scope of this post. If you’re using Linux and this sounds like a hassle (it is), don’t worry. It’ll be fixed in the final version of the game.
Let me know how you’re enjoying the game, and if you run into any problems. It still has a long way to go before it’s finished and balanced, but I hope you’re all having fun with it!