Apple finally got a grip and dropped the non-disclosure agreement (NDA) for released iPhone software. This was way over due. Now iPhone developers can finally share best practices and tools. Now there will be iPhone developer books and more.
Apple argues in an announcement on the Apple site that the NDA was necessary to protect Apple inventions and innovations. Apple has filed for hundreds of patents on iPhone technology and the company felt that the NDA added yet another level of protection.

Now Apple finally understands that the NDA has created too much of a burden on developers, authors and others interested in helping further the iPhone’s success - Congratulations!
Via the Apple site.