I think the use of "melody" is a slight misnomer - the article is really just talking about the potential number of different "SEQUENCES" of notes. The actual number of sequences which would result in anything that could be termed a "melody", rather than just a random cacophonous sequence, must be substantially less!

As to whether "Girls Just Wanna have Fun" counts as the former (a melody) or the latter (a cacophonous sequence) - well, that's a minefield I have no intention of entering!

Hang on, yes it is - it's the latter...
:-)