Except in this case you're not touching the book at all. If you write a
review for a book (much better analogy methinks), then your review is
obviously not an integral part of the book even though it's based on its
content.
Being an integral part (as in combined or derived work) has nothing to
do with usability. There are many other bits and pieces your executable
needs in order to function properly (or at all) but that doesn't make
your CPU microcode & electricity provider an integral part of the
program, does it?
Luckily, it doesn't really matter what you or I think that
"integral-ness" means, all it matters is how copyright law defines a
"derivative work" and whether a cryptographic hash is such a thing. Now
are you seriously arguing that a hash is a derivative work?
It's mere aggregation, but it's totally irrelevant because they could
just as easily change their approach.
---
fm
-