Apple doesn't make third party apps. If Vudu wants an apple tv app, they will have to make it. Apple only blocks apps that violate its TOA.
Or competes on the revenue side...If it weren't the case, VUDU would have an app for older versions of AppleTV just like Hulu or Netflix.
What you get on an iDevice is just a player and that's all that's needed on AppleTV yet there isn't one.