[feralchimp]

"files in the .ibooks format generated using iBooks Author"

That clause is ambiguous, and I wouldn't bet on it being interpreted in the sense your scheme would depend on.

You'd need "generated using iBooks Author" to denote which "files", where it's more likely to be interpreted as denoting which "format". That is, the clause disambiguates the format from any other format that may exist with the file suffix ".ibook".

ANYway, this EULA update is appreciated.