Well this is very interesting.
I was perusing twitter when I found this on The National's twitter page, so it's all above board, and legal, and comes from The National itself.
It's their iTunes U site which you can go to and download stuff about their productions for free.
There is four things connected with Frankenstein......the NTLive trailer, an interview with Nick Dear, an interview with Danny Boyle and Nick Dear, and something about man made creatures.
There's also stuff available for several other National Theatre productions, and lots of behind the scenes of The National too, and as far as I can tell it's all free.
This link should take you straight to the relevant iTunes page.