[hlasdjlfhalwjk]

An old version is available here: http://arclanguage.org/install

I assume the current version is still written in Arc (Paul Graham created the language) but differs from that version.

[krapp]

There is also anarki, the experimental public fork[0] of Arc and the forum. Like everything else, it differs from HN.

[0]https://github.com/arclanguage/anarki