Much of the HN codebase consists of anti-abuse measures that would stop working if people knew about them. Unfortunately.
There's a very old version of HN that pg published years ago (at http://arclanguage.org/). It would be nice to get that updated and maintained, but separating out the secret parts would by now be a lot of work. The time to do it will be if and when we eventually release the alternative Arc implementations we've been working on.
I'm open to doing that. It would just be a nontrivial amount of work and there are many nontrivials on the list.
Yes, there's now an Arc-to-JS called Lilt, and an Arc-to-Common Lisp called Clarc. In order to to make those easier to develop, we reworked the lower depths of the existing Arc implementation to build Arc up in stages. The bottom one is called arc0, then arc1 is written in arc0, and arc2 in arc1. The one at the top (arc2, I think) is full Arc. This isn't novel, but it makes reimplementation easier since you pack as much as possible in the later stages, and only arc0 needs to be written in the underlying system (Racket, JS, or CL).
It also shrank the total Arc implementation by 500 lines or so, which in pg and rtm-land is a couple enclycopedias' worth. That was satisfying, and an indication of how high-level a language Arc is.
There's a very old version of HN that pg published years ago (at http://arclanguage.org/). It would be nice to get that updated and maintained, but separating out the secret parts would by now be a lot of work. The time to do it will be if and when we eventually release the alternative Arc implementations we've been working on.