Buried deep inside the rules that Apple sets out for developers who write software for the iPhone and iPad is a clause that could be bad news for Adobe Systems.

Adobe, whose Flash video software is prominently not allowed on Apple's devices, is getting ready to release a new version of its flagship Creative Suite software. One prominent feature in the software can allow programs written for PCs or other phones to run on the iPhone.

But on Thursday Apple changed the rules about what tools people can use to develop these apps. The upshot: Adobe's forthcoming software is probably not allowed.

The language does not mention Adobe by name, but indicates that any program has to be written to run directly on the iPhone operating system-not for some intermediary layer of software. That sort of translation is essentially what Adobe is planning. (You can read the relevant sections of Apple's new restrictions at Daring Fireball, which first noticed the change and realized its consequences.)

Adobe said in a statement that it was aware of the new language and looking into it, adding that it was moving ahead with its iPhone tool. Apple didn't immediately respond to a request for comment.

If Apple does make it forbidden to develop iPhone apps with Adobe's new tools, it would exacerbate a spat between the two companies. Apple doesn't allow videos encoded with Adobe's Flash technology - the overwhelming majority of online videos - on its devices. Apple CEO Steve Jobs says this is because Flash is too buggy. But people outside of Apple say that allowing programs that use Flash on the iPhone, would give developers a way to build apps that can run on multiple devices-they wouldn't have to prioritize Apple's hardware as most do now.

Adobe's new software is that company's attempt to knock down that hurdle; developers could write the app in Flash and turn it into an iPhone app when they're done. The new contract language appears to be Apple's attempt to keep that barrier in place.