While I am not a lawyer and certainly no licence expert, I still find anything that borders to principles of law kinda interesting, and some of the arguments in this thread fail when judged against these principles:

The law most certainly does not care to differentiate between "non-functional or minimally-functional stub" and "fully functional stubs". The law might differentiate on intent though, but probably not any much when it comes to licences and copyright law. Either it's legal for all and every stubs that use a technique not clearly mentioned in the licence, or it is illegal for all and every stub that use that same technique.

The law will not go into evaluations like "the original library is useless". It's all about principles and technicalities, not quality and featurerichness.