I’ll bite. I have written a recursive DNS resolver. It’s buggy, mind you, it doesn’t handle improperly configured domains bug-for-bug the way BIND9 does, it doesn’t support IPv6 for resolving records (it can still resolve AAAA records, mind you), but it’s about 80 kilobytes in size, runs nicely on 32-bit systems, and does full DNS resolution starting from the root servers.

Does the fact I have written this resolver make me liable should it not block the domains they listed which may contain copyright infringing content? Am I now required to add these domains, and make them part of a mandatory block list? Will I still be held liable if people can still access these allegedly copyright infringing domains by modifying the source to my program?

Keep in mind that when Quad9 had a similar lawsuit in Germany, they blocked queries from German IPs, but the idiots said Quad9 was still liable because people could use VPNs in Germany to bypass their geoIP blocking.

Quad9 being forced to block these domains will achieve nothing. Will these copyright enforcers now go after Google for 8.8.8.8? Cloudflare for 1.1.1.1? Level3 for 4.2.2.1? Will they go after ISC for BIND? NLnet Labs for Unbound? CZ.NIC for KnotDNS? Me for MaraDNS? Even if they enjoin me from making a recursive resolver which can resolve these domains, that won’t stop anyone and everyone from forking my code (see also: Twitter trying to take down Nitter).