It sounds like you are asking about the tuner situation. Let me see if I can help.
The HD receivers from Dish will take both the satellite HD signal and over the air HD signals, and work with them just fine. They will then output a HD signal.
What this means from a TV standpoint is that you do not need to have a built in ATSC HD tuner in your TV. You can get an HD Ready TV without any problem. That is what I have. The only benefit to having an HD tuner built into your TV is that you could plug the antenna for OTA directly into your TV, but why would you do that? You would miss out on all the great DVR functionality for your OTA shows.
So unless you are planning on plugging the antenna into the TV directly, you don't need to have an internal ATSC tuner, you just need an HDTV ready TV.
As for if the receiver "has to be HD" I am not sure what you mean. If you are asking if your TV has to be HD to have an HD receiver, then no, it doesn't, you could still use the recevier, but you would of course not get an HD picture on your TV. You have to have an HD receiver and an HD TV to get the full benefit.
Hope that helps and answers your question.