Apple has stated that they will not allow 3rd party applications on the iPhone. Apple want’s to control everything from the top down. They’re not even supporting Flash or Java (I guess that would make it too easy for developers to bypass Apple’s control and offer applications for the iPhone).
http://www.starryhope.com/tech/apple/2007/10-ways-the-nokia-n800-is-better-than-apples-iphone/