He is not required to prove to you - or anybody else - that he has permission, unless challenged by an author or a publisher. Lets assume he does until you have proof that he does not and even if he does not there is a pretty good fair use argument to be made for out of print books.
To me it looks as if you have an axe to grind and will stick to your mantra, even though by all the available evidence this is done by a highly respected academic and completely out in the open, if it was done illegally (as in, with the full knowledge that authors/publishers would object) this is the most stupid way to go about it. It is your claim that requires proof, not the other way around.
When you get permission from the publishers, how on earth is it "piracy"??