I realize this is old, but as someone who has both ipad and iPhone, what you need to do is download it for the phone first, then look on the ipad under purchased items. Then you'll be able to download it. Or, if you have a Mac, go into the App Store and buy it, then upload it to your ipad.
Also, the app doesn't have a landscape mode. So your ipad will always have to be vertical to use the app. Which is, to me, very annoying.
