Hitch, I guess my response was unclear (or just plain poorly written) because I agree with what you said about out-of-copyright books.
I think it stems from different readings of the op's clarification:
<<actually the few the books I have obtained this way (all of 3) were all old out of print books and unavailable to buy which I was able to find in PDF format, >>
Some were interpreting this to mean "out-of-print but still in copyright" while I was interpreting this to mean "out-of-print and NOT in copyright". I've gotten several 150-year-old out-of-print books on an obscure subject from Internet Archives and they always indicate that they've checked the copyright status so that type of situation was my first thought when I read his comment. Who knows what he/she really meant, but it didn't seem right to automatically assume that he/she was doing something illegal.