Quote Originally Posted by Brandybuck
You should put in the exception notice, as mentioned in the second link jacek provided above.
IMO the exception is not appliable here, because it requires the owner of the opensource component (Trolltech) to acknowledge that.

I would also urge you to at least look around for a true Open Source alternative. Even if you like your chosen library the best, the ability to use an alternative gives you (and your users) more flexibility, and prevents you from getting locked in to a proprietary solution.
I second that. And if you provided a free (not as in free beer) alternative, then you can make that proprietary library optional and you won't break the GPL licence.