As the title say Xenonauts is on Steam http://www.xenonauts.com/category/news/ Will have to look into this to see if I can get it downloaded, after my disappointment with the XCom game this may just be the ticket.
Its pretty good ufo:AI is a good open source alternatuive
Must have a look at that OS one some time.
Looks like the games coming out of early access on Steam. http://steamcommunity.com/games/223830/announcements/detail/1351390965641409209
We have now released Xenonauts V1.0 on the Stable branch, which marks the end of formal development for Xenonauts. This is effectively the final version of the game, minus any stability patches that may be required.
Official release and leaving Early Access for the game is in about two weeks (tentatively pencilled in as 16th June), but the remaining time is mostly going to be spent on sending out review copies, the PR around the launch, porting to Mac / Linux and getting the Kickstarter rewards sorted out etc.