It's different, yes. The HN implementation is called clarc. PG suggested we spell it "clerk" as a joke on the British pronunciation of the latter, but I chickened out.

I talked to one of the Anarki devs (or at least someone who uses it) about possibly open-sourcing a version of clarc which would run the original open-sourced version of HN, but it's a bit hard because the implementation would require some careful surgery to factor out the relevant parts.