Qt is quite nice, but it may have license issues unless you buy a copy.
Also, you didn't state what platform you need it to work at, so you might want to check supported platforms too
Qt doesn't have any real license issues - at least, not according to my decently thorough but non-lawyer opinion of the matter.
You can use Qt for commercial projects just fine as long as you:
A) Dynamically link instead of statically link (no problem whatsoever for desktop applications; might be a problem for mobile releases, but people have workarounds for that on some platforms)
B) Release any sourcecode changes you've made to Qt itself (your own project can remain close-sourced)
C) Make sure that you distribute Qt's license alongside the Qt libraries (which most 3rd party libraries (including the ones you are already using) require and isn't much of a hassle)
Qt is managed and developed by an opensource community, and Qt itself is opensource under the LGPL license. If you're not familiar with opensource licenses, my general rule of thumb for indie commercial game development is GPL = bad, LGPL = good, zlib/libpng/MIT = better (other peoples' views differ). You can read any of my other posts, or dozens of other peoples' articles on the net, for more detailed opinions on the matter, so I won't derail the thread by going into further details here. More recent versions (the past year or more) of Qt are under LGPL3 instead of LGPL2, and people thought that might be a problem at first, but it isn't, so we're good.
Now, there is a company (Digia) who makes its money off of licensing alternative commercial licenses for Qt, and providing Qt-related support. Because they manage the official Qt website portal, they write the portal in such a way as to manipulate peoples opinions of it, to drive commercial license sales (granted, I don't know their actual motives, but that's what it looks like), so they ask a bunch of misleading questions and so on, designed to stir up doubt in your mind, but because the software is already open sourced, they can't do a thing about people using it commercially for free (Note: Digia wasn't the creator of Qt either, they just bought the licensing/support business from Nokia (who bought Trolltech, the original Qt creators); they do help steer Qt development, though, but it's heavily community-driven).