AI War and Tidalis are on totally different engines.
AI War runs on our custom SlimDX/.NET engine, which is limited to Windows or emulations thereof.
Tidalis runs on the Unity 3D engine, which allows us to create both Windows and Mac builds (it also allows extension onto the iPhone and the Wii, and later versions will support the Android, the PS3, and the XBox360; but all those have additional fees involved).
The Unity team has been asked quite a bit for Linux support, but I don't think they have any plans for it at this point.
We'll be attempting a port of AI War to the Unity engine later this year, perhaps July.