From what I understand, Apple is a distributor - not just the original developers.

Because Apple is distributing they have the same responsibilities as any distributor to provide the source code and allow the code to be shared.

And making people worried about the GPL shouldn't be a priority here. The GPL isn't a free-for-all license - its a very specific license which, while granting a lot of rights, also has a lot of requirements. Anybody distributing code with such a license needs to make sure they fall in line.