I think Orelly themselves put these for free back in the day in its own domain. I have to seek archive.org in order to be sure.
I tought that because most of the books are outdated (15 years on IT it's an epoch), albeit the sed/awk/perl/*sh and Sendmail books are still godly useful.
I actually received a free book from O'Reilly once for pointing out the exact site you mentioned, so their lawyers could address it.
If you want these books very cheaply, the Perl CD Bookshelf usually sells for about $5 used. You get Perl in a Nutshell in print and a bunch of the other books on CD.
A better introduction to Perl these days is Modern Perl, which is available to read online for free or you can pay for a print book. http://modernperlbooks.com/
I don't know about you, but many of us on HN make our livings with things protected by copyright, trademark, and sometimes patents. Supporting the framework that enables our livelihoods is not a moral judgment. It is a practical concern.
Also, there are legal issues over promotion of pirated content.
Also, there are ethical concerns over pirating content that is easily and cheaply available legally.
Also, I said "Please" and didn't force anything on anyone.
Also, under a strict interpretation posting directly to pirated material is likely a violation of the Terms of Use for HN. https://www.ycombinator.com/legal/#tou
I tought that because most of the books are outdated (15 years on IT it's an epoch), albeit the sed/awk/perl/*sh and Sendmail books are still godly useful.