Based on the teaser images, it seems likely that all of these titles will also make their way to the Mac. This leads us to believe that Valve has ported their Source game engine over to the Mac, which would allow any future games based on this engine to be easily launched for the Mac. Alternative [sic], Valve could be using Transgaming/Cider for the translation.
The Significance of Steam and Valve’s Games for Mac - Mac Rumors
This is a big deal for gaming on the Mac. If Valve has indeed ported or rewritten their Source game engine for the Mac, it’s an even bigger deal. Not only would Mac users have access to a great game distribution platform, but game developers would also have access to a game engine that could easily target Windows, Xbox 360, PlayStation 3 and OS X. It would make the case for developing Source-based games for the Mac a no-duh proposition.
Plus, I don’t see how Valve could justify this hype if all they’re doing is using Cider to act as a graphics translation layer. That’s nothing new, and anyway, who would want to base an entire business venture on another company’s inelegant graphics translation product? I hope Valve sees it the same way.
Update 3/8/2010: They do.
Based on the teaser images, it seems likely that all of these titles will also make their way to the Mac. This leads us to believe that Valve has ported their Source game engine over to the Mac, which would allow any future games based on this engine to be easily launched for the Mac. Alternative [sic], Valve could be using Transgaming/Cider for the translation.

The Significance of Steam and Valve’s Games for Mac - Mac Rumors

This is a big deal for gaming on the Mac. If Valve has indeed ported or rewritten their Source game engine for the Mac, it’s an even bigger deal. Not only would Mac users have access to a great game distribution platform, but game developers would also have access to a game engine that could easily target Windows, Xbox 360, PlayStation 3 and OS X. It would make the case for developing Source-based games for the Mac a no-duh proposition.

Plus, I don’t see how Valve could justify this hype if all they’re doing is using Cider to act as a graphics translation layer. That’s nothing new, and anyway, who would want to base an entire business venture on another company’s inelegant graphics translation product? I hope Valve sees it the same way.

Update 3/8/2010: They do.