The new iPhone Developer Program License Agreement states the following:
(e)You will not, through use of the Apple Software, services or otherwise, create any Application or other program that would disable, hack or otherwise interfere with the Security Solution, or any security, digital signing, digital rights management, verification or authentication mechanisms implemented in or by the iPhone operating system software, iPod touch operating system software, this Apple Software, any services or other Apple software or technology, or enable others to do so; and
(f) Applications developed using the Apple Software may only be distributed if selected by Apple (in its sole discretion) for distribution via the App Store or for limited distribution on Registered Devices (ad hoc distribution) as contemplated in this Agreement.
This means that registered developers can no longer jailbreak their own phones or help others to jailbreak their phones. Developers are also forbidden from using the iPhone OS, SDK, and any other developer tools to create applications that are distributed anywhere but the App Store or via Ad Hoc distribution