Found in 2 comments on Hacker News
Wayback Machine has been working for the past few days, look: https://web.archive.org/web/20240607220047/http://www.oreill...
It looks as though they killed the page sometime between June 7th and June 26th, although the page on June 7th seem to try to redirect to “https://oreilly.janrainsso.com/static/server.html?origin=htt...

https://web.archive.org/web/20240607220047/http://www.oreill...

Definitely perplexing, I can’t find the reason to kill what appears like a simple HTML page unless they’ve killed the project entirely.