"It's not two copies of the game, it's the same game"
"The goal is to give a Portal 2 customer access to their game on as many devices as possible. We introduced this notion when we launched Steam Play for Mac and PC games in the spring of last year," Lombardi explained. "Giving a PS3 owner of Portal 2 the ability to also play their game on the PC and Mac is an extension of this philosophy. From our perspective, it's not two copies of a game; it's the same game, but with Sony's help we've worked out a method to allow that Portal 2 PS3 customer to also play their game on the PC and Mac."
Which of course brings up an obvious question: was this option also offered to Microsoft? "It is achievable from a technical standpoint, yes," he told Ars. Allow us to speculate for a moment and say that Microsoft most likely doesn't like third-parties using their own online tools, nor would it agree to giving up any control of patches or updates, an issue that has long been a sticking point between the two companies.
Now that Steam is running on the PlayStation 3, the service may be added to other games as well as Portal 2, but Lombardi refuses to give any specific news. "We are hoping other titles will benefit from the Steamworks tools and services we've created for Portal 2 PS3, but we don't have anything to announce today."