Here was the response from Scott:
Hi Roy -
The material is not in the public domain, at least not all of it. However, the work is rare enough that no one has challenged me in the number of years I've had it up, and I would pull it down if I did get a complaint. Occasionally, I get a thank you for making the stuff available.
If you're comfortable with linking to the main site page, as opposed to individual books or mirroring, I'd be fine with that.
I'll check out your site, and thanks for your email -
Scott
I'll see if any of these are older than any of the same title we have on GAC (and/or DCM) and figure something out.