The world whined and Steve Jobs listened. Aimed for a February 2008 release is the iPhone/iPod touch third party application SDK as revealed in a letter Steve wrote on Apple’s website:

“Let me just say it: We want native third party applications on the iPhone, and we plan to have an SDK in developers’ hands in February.”

Reason for the delay is that in order of making the iPhone more open while keeping it secure from viruses has been a challenge. They’re taking their time, and doing it right. Jobs also mention that Nokia uses a digital signature system for their apps and it can be traced back to a known developer. This might hint that Apple might pick up a similar digital signature system for their app verification. There’s no detail on the SDK at this time, but as long as Apple doesn’t ibrick the devices on every update, everyone would be happy.