I bet there is a clause somewhere that they can revoke the "licence" they give you. Between the lines it can be read as "if you want to use he 'Office UI', you need to have a poisson pill ready should you ever do something we won't like". Imagine such UI components going in any of front line 3rd party applications such as Photoshop, AutoCAD or whatever. "Oh, we the Microsoft are releasing a new crappy graphics application and by pure coincidence at the same time we regret to inform that you have to stop selling Photoshop becuse we have just decided you are in violation with our Office UI agreement".