iPod Observer recently spoke with someone at Apple and was able to get a little more information about renting HD movies using the new Apple TV software. The basic gist is that HD movies can only be rented, not purchased. Standard definition movies can be purchased, but high-def movies can’t.
The movies are streamed directly from Apple’s servers and displayed on your TV. Nothing is downloaded to the Apple TV’s hard drive or your computer, if you’ve got one connected. This is most likely to prevent piracy, according to the site. “It’s likely that these conditions were set by the studios to protect HD movies from ever residing digitally on the Apple customer’s Apple TV, being unlocked, and possibly pirated.”
Apple Clarifies HD Movie Rental Operations [iPod Observer]