Thanks! I'm using the LGPL version of Qt, since I'm not changing Qt's own source code I can release my app has closed-source easily with dynamic linking. I could also release it with static linking with no problem (in my understanding), if I allow people to download the object files as well so they can link them to any version of Qt they want (but that's a bit too much for now).

Thanks for your suggestion, I'll consider it. But what do you mean by ugly flashing? Is it the instant background change that turn you off?