The QT licensing seems very anti-learning, because afaik anything you develop with it can only be commercial if and only if its entire development was done while using a commercial license.
Ethics aside, if you're new to QT, play around with it using the non-commercial license (since you obviously wouldn't know at that point if you could do something commercially viable) but you end up developing some rough prototype that might be a worthwhile stepping stone to a commercial product, and then at that point you buy a commercial license, could QT tell if you incorporate parts which were developed before having the commercial license?