Oddbean new post about login | logout I don't think so, but you would have to ask @brugeman I think it just pulls your long form content into some framework that applies a theme. Supposedly you can self-host, but I have not tried.
The proposed NIP is https://github.com/nostr-protocol/nips/pull/1348 There is an event describing your site and which kinds/tags to include, there are theme events, etc. And then the website engine pulls your notes matching the filters.