Taken from the FAQ:

Achron is a multiplayer real-time strategy (RTS) war game designed around the ability to time travel anywhere along a timeline. Jump back in time to save that production facility, or add a flanking maneuver to an attack! It's entirely up to you.
A Linux client should be released around 15th March. They say they have 95% of the engine code compiling cleanly on Linux atm.

It's available for pre-order at this time.