InterNetNews, an ISC-licensed NNTP server, is still seeing active development apparently.
Andrew and I were talking about it last week at one point and really, if you want to have a nice asynchronous set of conversations with a small group of people all working in a similar space, having a nice quiet NNTP newsgroup on a private news server for your membership ain’t a bad way to go.
None of the deliverability nightmares of modern email listservs, none of the administrative headaches of running some web forum package or matrix or a private fedi server or any of that crap, nice threaded conversations with easy to manage history storage on the server side that’s not going to go exponential on you any time soon. Why not NNTP for thee?
Everybody gets to use their client of choice, possibly an email client they already use and like, and check in on their own schedule and reply in their own time after due consideration with no push notifications. Doesn’t it sound nice?
You can absolutely run NNTP servers that don’t federate any newsgroups to any other servers. You can just do that.
@djsundog and, in fact, enabling federation with any given server requires intentional manual out of band action, by my understanding.