Well, it looks like Apple is looking for a way to open up the iPhone in the near future....

http://www.engadget.com/2007/05/30/iphone-to-get-third-party-apps/

I would imagine that the third party apps would have to be officially licensed and endorsed by Apple to run on the iPhone....

The app would have to follow certain guidelines such as programming the app to follow more energy conservative measures (not polling the internet as frequently as its desktop version would) or other measures such as not being able to screw with other data files on the iPhone or install haxies or OS hacks that would modify OS behavior....

Games being developed for the Xbox 360, PS3, and Wii have to be certified as well to run on their platforms.

It would probably be easier for the developers since all the iPhones would have the same exact hardware specs and OS. It's harder to develop NightHawk for Mac and Windows 'cuz there are a variety factors to support such as different operating systems, different CPUs (G3, G4, G5, Pentiums), and different operating systems (Win XP, Vista, Panther, Tiger, Leopard).

The developer knows what is on the iPhone and develop for that hardware/OS set..... This is why it is easier to develop for game consoles as well.... All PS3s run pretty much the same. All Xbox 360s run the same. And all Wiis run the same. The only notable change would be the internal hard drive size....

So let's hope Apple can open up the iPhone sooner rather than later... Very Happy