Qt comes in both GPL (which I'd never choose, and there is no reason to) and LGPL (which is the one you can use for open-source and closed source/commercial both).
I am not a lawyer, but the general consensus for LGPL is that as long as you link dynamically, don't modify the source code, don't rename the lib files, put the license somewhere* and (some say this is mandatory, most say it isn't) make the source code of the LGPL-licensed software (so not your software) available somewhere, you are fine.
It really is not much to do and almost every software that does anything with audio/video manipulation does that for FFmpeg, for example.
Besides, this wouldn't even affect the editor in Urho3D since that would be open source anyway.
wxWidgets has some very weird kind of custom license, which seems to be a more permissive variant of LGPL allowing you to modify its source code as well.
But I see no reason to use wxWidgets. It isn't exactly lightweight, either and not as versatile as Qt. And it doesn't have an editor that could rival Qt Creator even nearly.
I tried working with wxWidgets before, more than once. But it always ended with hitting some brick wall that doesn't exist in Qt...
The only reason not to use Qt would be if someone wanted to have everything (including Qt) statically linked for the editor.
But why would anyone want that? To hide from other programmers that he did not write an entire interface library for every platform himself?
[size=85]*You know, those "license" buttons in software that nobody really clicks on? Like that [/size]