iPhone is not a device its a computer that just happens to be the size of one, and make calls. The SDK can go either way it all depends on the way apple plans to implement it.

In one scenario all the jailbreakers and unlocker and hackers will be able to create legal apps and the software market on the iphone will flourish

in an other scenario apple will lock down the apps with watermarks and itunes will erase unauthorized apps from iPhones, the hackers will still find a way around but it will stall flourish-ment