Thanks so much for your answer. For an embedded device, what's a recommended way to make it so my users could change out their Qt libraries as required? From my inexperienced POV it sounds horrible - I'd have to create some kind of custom update for them, provide them the tools to build Qt, and probably something else I'm missing in my understanding of the LGPL.
Also I was hoping to use Qt5 if that makes a difference (QML seems nice..).
Also I was hoping to use Qt5 if that makes a difference (QML seems nice..).