Update: A Dish spokesman confirmed that the OTA tuner does sell for $30 and can be purchased at MyDish.com. He added that the necessary software to operate the module should have already been pushed to Hopper receivers. Customers will still have to purchase exterior or interior digital OTA antennas on their own to complete the set-up.
Here's an illustration of how the module connects with the Hopper via a USB interface:
— Jeff Baumgartner, Site Editor, Light Reading Cable