What is relevant is that they should check the license of software they distribute through the app store, and make sure that they, themselves, comply with it.
If the license of the software they accept is under the GPL, Apple should realize they cannot distribute it in a way that requires the end user to comply with additional restrictions (such as the mentioned limitation of installation on five devices), and should either change their policies and do not impose any such restrictions, or, doing as they often do, and not accept the software into their store.
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