As a modder for Oblivion, I can tell you with 100% certainty this is an outright ripoff.
The bookshelves are the dead giveaway; the placement of the books, urns, and "clutter" are near-impossible to totally replicate due to the havok physics and the micromanagement of the items. They've broken into the Oblivion Construction Set and copy/pasted *everything*.
EDIT - Or Bethsoft has allowed this to happen on some level. I'm not a business guru, but I know my bookshelves in Oblivion. This comment was edited on Jun 11, 13:44.