Steam for Mac is coming in April. All available Source Engine titles will run natively on Macs. If you already own them for your PC you’ll have access to them for your Mac.
There’s a lot of excitement, but I think this part is huge news:
“Checking in code produces a PC build and Mac build at the same time, automatically, so the two platforms are perfectly in lock-step,” said Josh Weier, said Portal 2 project lead in the press release. “We’re always playing a native version on the Mac right alongside the PC. This makes it very easy for us and for anyone using Source to do game development for the Mac.”
Sounds like what Valve is going for is something like: Steam is to Games as iTunes is to Music.
And if that’s the case, if you’re a developer why would you use any other game engine?
I think Valve is about to sell a lot more Source licenses.