http://arclanguage.org there is a tar file under the install link and the news source is in there. Others in the community have ports etc on github. Check out the forum on the arclang site.
We now finally have search for HN, thanks to Octopart, who've been working on it for a while as a test of their new search database, ThriftDB. You'll see a search box at the bottom of most pages.
Sorry this took so long. For a while we hoped to implement our own search, but it became apparent that would take a lot of work to do right. So we were delighted when Octopart decided to get into the search as a service business.