[jacquesm]

That's all fine and good but Xerox is no longer in the business of selling this book and does not suffer any harm from the reproduction, neither do the authors.

It's a bit like public libraries, which also 'hurt' book sales, and there the books might even still be in print. The Smalltalk 80 Blue Book is an important part of computer history, the more copies there are of it, digital or otherwise the better.