The Usage Rules shall govern your rights with respect to the Products, in addition to any other terms or rules that may have been established between you and another party
Now:
...unless the App Store Product is covered by a valid end user license agreement entered into between you and the licensor of the App Store Product (the "Licensor"), in which case the Licensor's end user license agreement will apply
So either GPLv2 is a valid end user license agreement, or if it isn't, one just needs some out-of-bound mechanism that users and developers agree on GPLv2.
Apple changed App Store terms. Previously:
The Usage Rules shall govern your rights with respect to the Products, in addition to any other terms or rules that may have been established between you and another party
Now:
...unless the App Store Product is covered by a valid end user license agreement entered into between you and the licensor of the App Store Product (the "Licensor"), in which case the Licensor's end user license agreement will apply
So either GPLv2 is a valid end user license agreement, or if it isn't, one just needs some out-of-bound mechanism that users and developers agree on GPLv2.