"I think sometime later this year we will find a way to let third parties write apps and still preserve security. But until we can find that way, we can’t compromise the security of the phone. Nobody’s perfect, but we sure don’t want our phone to crash. We would like to solve this problem, if you could be just a little more patient with us, I think everyone can get what they want." Jobs said.
Jobs also confirmed the iPhone will indeed be running a full version of OS X with a different user interface tweaked to work with a multi-touch screen. It is only a few more weeks until the launch of the anticipated iPhone in late June, only then all the speculation surrounding it will finally come to an end. You can read Steve Jobs interview at the AllThingsD website.