I'm no expert in licensing issues, but it's obvious that not every piece in a licensed set is a licensed piece, otherwise we couldn't get 2x4 black bricks anywhere because they appear in Hogwarts (to use an extreme example). I wouldn't think they would need to license something like the dragonlet. It's not uniquely identifiable as an HP entity outside of an HP set. The only reason you know it as Norbert is because you know the set it came from. I didn't know it was used in an HP set so I didn't associate it with Norbert when I got the Wizard. However, drop a minifig with a lightning bolt scar into a random scene and almost everybody will think Harry Potter immediately, so I'm sure that head is licensed.
I know you said that was a bad example, so in order to generalize my explanation a bit better: I don't think it has to licensed if it can't be explicitly identified as an element from the licensed franchise.