[modernerd]

The RSS 2.0.1 spec at https://cyber.harvard.edu/rss/rss.html is essentially dead, or “frozen” / “settled” as it says there.

2.0.1 was published in 2003 and I don't expect to see a 2.0.2 or 2.0.3.

The ambiguities you mention are real, though. “The url must be an http url” is one that feed validators would adhere to very strictly, for example, rejecting HTTPS URLs as invalid[1], which even caused Apple's Podcast submissions process to reject feeds with HTTPS URLs in them at one point (I was employed at the time by a company that hosted podcasts, and we had to work around it by rewriting URLs to use HTTP).

I received a reply from the spec's author to my email suggesting they update the spec to clarify this (“of course you can use HTTPS”) but the spec itself was never updated and I would consider it unmaintained at this point.

Atom and JSON Feed are good alternatives. Atom because it has fewer ambiguities and JSON Feed because it has an open GitHub repo[2] and was updated in 2020.

[1]: https://github.com/rubys/feedvalidator/pull/12

[2]: https://github.com/manton/JSONFeed