Phoronix: PathScale Working On DogFood, A New Dev IDE
PathScale is working on a new project that is internally dubbed "DogFood", it's a new integrated development environment (IDE) based upon Qt Creator but with a greater focus on C++ and other new development concepts...
You'll be modifying QtC and create a derivative, not link against it (it's not a lib), so the obligations are the same as the GPL.
I'm not sure how familiar you are with QtC design, but almost everything is pushed to a plugin. You're right that any core QtC changes should go upstream, but they made this pretty commercial friendly. This is not to mention the other licensing options which are available. I'm not alluding to anything, but I'm trying to state facts to avoid FUD.