Contrary to popular misconception, you don't have to install all of "KDE" (you can't download a community) or a monolithic kdelibs (no longer exists) just to develop KDE software. That's especially true if you just want to use just a few KDE Frameworks for your Qt project. You don't even need to compile anything at all! Except for your own project, of course. Granted, there are a few ways to go about using KDE libraries for your application so this page lists some of them, depending on your situation or need.