Well, I can't see why Trolltech (the owners of Qt) would object.
Presumably the main reason that you would want a Qt skin for Windows application running under Wine is that you run several other Unix applications using Qt...
So I can't see why they wouldn't give us special permission if we for some reason would need it...
I'm not sure it's quite that simple though. IIRC Qt/KDE themes use the Qt drawing primitives (like gtk skins do with gdk). Unfortunately, Qt/Win32 is not free software, so we'd have to stub out Qt with Win32 equivalents in order to allow Qt skins to draw correctly. As GDK is already ported to Win32 though, that'd be easier to use.
I'm sure if somebody was motivated enough they could do so, and we may need to stub out Qt anyway for KHTML at some point. But it's a lot of work.
The alternative a GTK skinned only Wine would not benefit them at all, quite the opposite.