Got the QT IDE installed on Windows, and built an application, in order to find out about dependencies, redistribution etc. It seems that you basically have to redistribute three core dlls, along with (possibly) some MS VC++ dlls, in order for apps to function, but you're allowed to redistribute the QT dlls; as far as the MS VC++ dll(s) are concerned, we'd have to see under what circumstances they're needed, where they're likely to be missing from a system, and whether it's practical to redistribute them. QT seems to work OK on Windows 7, although it's not supported formally on that platform.