Ars Technica is reporting, and posting the relevant legal language to back up, that the iPhone Developer Program License Agreement now contains language that says:
registered developers can no longer jailbreak their own phones or assist others in jailbreaking their phones, including (but not limited to) working on projects such as QuickPwn or PwnageTool. Developers are also forbidden from using the iPhone OS, SDK, or other developer tools to develop applications for distribution in any way other than the App Store or Ad Hoc distribution—which of course rules out distribution via Cydia, free or otherwise.
Of course, this won't prevent iPhone Dev Team from working on future jailbreak-related projects, but Ars rightly points out it may make legit iPhone developers hesitate in helping them out. From Apple's point of view, this is understandable (they want control of their platform and revenue stream), but from the point of view of certain types of developers and technology enthusiasts, it's untenable.
However, it remains to be seen what, if anything, Apple can or -- more importantly -- would do when it comes to enforcing this agreement.