Looks like a great project, and one sorely needed by people like me who find themselves trying to get hold of old books they can't get in their local library and that are too expensive to buy secondhand.
As far as I know Standard gets their raw ebooks from Project Gutenberg which has a vastly greater collection of public domain works. What they're doing is typesetting them for the average reader. But if all you're looking for is just the content, Gutenberg is the place to look for ethically clean copies.
The shadow libraries such as Anna's Archive are a treasure trove of old books, and you're not breaking any imaginary law by downloading old books which are out of copyright.
The internet archive's open library will also link to Standard Ebooks (and Gutenberg and a few others) if a version exists of a book you are looking at e.g.:
> A work that is a mere copy of another work of authorship is not copyrightable. The Office cannot register a work that has been merely copied from another work of authorship without any additional original authorship. See L. Batlin & Son, 536 F.2d at 490 (“one who has slavishly or mechanically copied from others may not claim to be an author”); Bridgeman Art Library, Ltd. v. Corel Corp., 36 F. Supp. 2d 191, 195 (S.D.N.Y. 1999) (“exact photographic copies of public domain works of art would not be copyrightable under United States law because they are not original”).
Certainly! If you add my latest Kirk/Spock slash fanfic to the end of the text, then that is transformative, so the resulting PDF is covered under copyright.
But you wrote "scan". Adding an OCR'ed text layer, or doing manual proofreading and layout ("sweat of the brow") is not sufficiently transformative to have copyright protection.
And we were specifically talking about scans of old books stored in shadow libraries.