Here's what I have found on the question:
Can Google Groups be used as a newsserver?
No... It's designed as a web-interface.What's a good free text-based news server?
Eternal September... and they retain 4 years of text data.Can we get postings from further back?
Possible. Various low-cost pay services advertise higher retention.
In particular, Agent Premium advertises 3300 days retention for text-based newsgroups -- that's just under 10 years, so to about 2005 -- UPDATE: Just tried this -- indeed, they have postings dating back to July 2003 -- 11 years ago. As another alternative, Derkeiler.com also holds text-based newsgroups back to 2005 (about 10 years), but does so in a web-browseable archive, which makes using a newsreader difficult.Can we get hold of anything older than 10 years?
Yes, but it's not easy. Apparently, Google Group archives go back over 20 years, but the problem is (quote) "that it’s hard to just browse a newsgroup – everything is search oriented, not browse oriented."
You can verify that the archives go back to at least 1990 by searching forJulian Noble
incomp.lang.forth
and sorting by date (note: you'll have to scroll down quite a bit...) (A bit of Google Groups history -- apparently Google Groups is the moved and renamed fate of DejaNews, a company Google acquired in 2001.)
(thanks to Journeyman G., Michael F., and Frank T. for their helpful comments)