Apple is taking a tougher stance on what its iPhone developers can and cannot do with the updated software development kit.

Developers have to sign an agreement if they want to create content for Apple's App Store, and this has been a point of contention before because of some of Apple's policies. But most developers complied because the App Store has seen more than 800 million downloads in less than a year, and it can be a potentially lucrative market for mobile app creators.

The latest version of the iPhone Developer Program License Agreement adds a few new clauses about what developers are not allowed to do. This now includes "jailbreaking" a device, helping to jailbreak, or distributing apps in ways other than the App Store. Jailbreaking gives developers access to the Unix core of the iPhone OS, and it enables users to do things like run apps in the background, change the home screen theme, and record video with the camera.

"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," the agreement said, according to a copy obtained byArs Technica.

This new clause has relevance now because groups of developers have created unauthorized alternative online stores for iPhone apps. The biggest is the Cydia Store, which is made by the developers of a popular iPhone jailbreaking software.

While the new clause likely won't stop the dedicated group of "underground" iPhone developers, it will likely make most mainstream content creators wary of the jailbreaking community because they risk being cut off from the App Store.

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