All: apologies for the interruption, but don't miss that there are multiple pages in this thread, with over 2000 posts by now. You have to click through the More links at the bottom to see them all. Later pages have all kinds of stuff that is just as interesting. It's kind of incredible.
(We intend to get rid of pagination once the next implementation of Arc is ready.)
Replies to this top comment have been quite a job to juggle. My approach has been to reply and then detach them, so as to minimize distraction at the top of the thread. Unfortunately, that has led to the same questions being asked over and over, so I'm going to move all the replies underneath this stub, and then collapse it. The reason for a stub root comment rather than just collapsing all the replies is that a list of dozens of collapsed replies would take up most of the page.
I'm also going to partition them by topic, since there are so many.
If you want to reply about Arc, do so here.
Is Arc open source?
Arc has a public fork called Anarki[1], which is built on Racket[2]. The Anarki version of the forum differs from the Arc forum, which differs from HN's own custom instance, which is closed because of various YCombinator business reasons.