Given we now have a live Windows GVEdit user on hand, it might be worth asking the question: @Olexa would you be OK if Graphviz required you to install the Qt libraries yourself?
Our main barrier as @magjac pointed to is that the legal requirements for distributing Qt with Graphviz are a little cumbersome. From a maintenance/liability standpoint, I would like to avoid the whole thing and simply depend on them being already installed.