Apple’s “one app” model is a big part of the mobile user experience that would have to be quickly jettisoned. While Apple’s iWork integration, announced at January’s special event, points at greater desktop/iPhone OS file system integration, the iPhone OS’s one app at a time paradigm simply doesn’t work for a multi-purpose, multi-tasking flexible desktop environment. And that’s not the only big change that would need to be made. Consider the whole question of each mobile application’s GUI needing to fit the device. Desktop users are more comfortable with flexible view sizes in a multi-windowed environment. Terpstra says, “It would take too many concessions to translate the current interface standards of the iPhone OS to desktop use.”

That doesn’t mean that the two platforms can’t share libraries. Already, OS frameworks — the precompiled libraries of routines that OS X developers on both platforms link to to gain access to Apple-supplied functionality — are growing closer. Under the hood, iPhone OS and Mac OS are essentially running the same OS, although the specific implementation details differ by platform. But Terpstra maintains that there are intrinsic limitations in that arena as well. He writes, ” I don’t see the iPhone, Apple TV and OS X ever all sharing a full code base. It would overpower mobile devices and underpower desktops. No one would be happy.” That’s the consensus here at TUAW as well.