This is something HN should just do anyway; that is high rep users flag a source as paywalled, and going forward the submitting user gets an alert with suggested alt links. No idea why HN isn't open source with an open source API to insert data too.
They take a pretty conservative approach to adding features.
They do have an API: http://blog.ycombinator.com/hacker-news-api
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API is read-only; API should be "full service" and the first interface to HN, not a supplement.
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Yeah, whole ARC (aka PG) thing is an issue too; FYI, those install direction are dated, here's the info: http://arclanguage.org/user?id=akkartik
PG doesn't even appear to be actively involved in ARC anymore: http://arclanguage.org/user?id=pg
Find it hard to believe if YC funded a startup like HN that they wouldn't require an explanation of why ARC made sense as the language of choice.