May 12, 2010, 8:03 AM — Today is a good day for Mac gamers, because today is the day that Valve's Steam service is scheduled to launch on OS X. Valve first teased this launch back in March with images of Half Life 2's Alyx hurling a crowbar at a movie screen in a way that brought Apple's old 1984 ad to mind.
Sadly Alyx isn't going to be part of the launch ceremony, but two games will be available today: Valve's own reality-bending Portal and Runic Game's dungeon crawler Torchlight. Both, I can say from personal experience, are really fun games and worth buying.
Of course at some point you may have already bought these titles for Windows. If so, you've already purchased the Mac versions, too. Since a game is tied to your user account, any Valve title (they can't force other publishers to provide the same offer) that you own can be run on any computer you're logged into, assuming that computer is running a compatible OS. This new licensing scheme is called Steam Play, and that was a long way of saying that when you buy a cross-platform Valve game, you get it for both platforms, and that offer is retroactive. It would appear that Runic Games is offering the same deal with Torchlight, though we'll have to wait for the launch to be absolutely sure.
Valve is adding OS X support to its Source engine for any developers working in it, so in the future Mac versions of Source games should be at least somewhat common. After today, Valve plans to add new games to Steam Mac every Wednesday. Beta testers of the Mac Steam Client say that Team Fortress 2 is playable in the beta, so we might get that today as well.