Earlier quoted context omitted.
Since Apple completely controls the App Store and reserves the right to refuse any app for any reason (and have shown time and again they are willing to exercise that right), how could this possibly be unenforceable? It is their way or the highway. What is or isn't enforceable is entirely up to them. Note: I am in no way saying that Apple's stance on this situation is a good one or not, in face, absurd. The iPhone 3G…
Unless they start auditing source code and everyone's entire development process, there are lots of ways in which such a rule could be violated that would be completely undetectable (and some cases that would be easily detectable too).
What this will absolutely stop is Adobe calling out developers who have added apps to the app store compiled with CS5. Those apps created that way will also be unable to move upwards to the new OS version. I would imagine it will also completely stop Adobe and others from any development on any OS 4 bridge because they would have to agree to the license to test against the actual SDK and they can't do that without legal problems.