Wow, if that OPD includes the decryption information for all the copy protection schemes, including CSS, AACS, BD+, Java, Screenpass, Playlist, etc, then I have absolutely no problem with 400 MB, if that is true. That's small enough to fit on a CD. I would have expected it to be so much larger from what I've heard in the past, and people speculating that it would be massive.
400 MB is nothing. Heck, I wouldn't mind if it was 4-8 GB. The size of your average DVD ISO.