Whoops, that's Anarki, not Arc.

pg's and rtm's original arc3.1 is on the "official" branch: https://github.com/arclanguage/anarki/tree/official

news.arc is the old HN source code. You can run it by following the steps in how-to-run-news.

(Run it with "mzscheme -f as.scm" though, not mzscheme.)