I think the (anonymous? I can't find a name) author of the OP slipped slightly at the end of that otherwise-impeccable sequence of quotes. That last comment (https://news.ycombinator.com/item?id=21546438) was responding to a question about open-sourcing the entire HN codebase, not just the Arc implementation.

Open-sourcing HN wouldn't work because of the anti-abuse stuff, etc. But open-sourcing the Arc implementation (i.e. Clarc) would be much easier. The way to do it would be to port the original Arc release (http://arclanguage.org/) to Clarc. It includes a sample application which is an early version of HN, scrubbed of anything HN- or YC-specific.