I believe we accomplished all of this using some crazy LotusScript. We pushed really hard to get our product out before Lotus could release Instant Team Room.
We spun off every tenant as a replica of a Lotus Notes database template (my lingo might be wrong, since 20 years has passed). People, at that time, however, hadn't quite warmed up to the concept of subscription software though.
[1] https://www.cnet.com/news/free-site-offered-with-groupware/
[2] https://books.google.ca/books?id=jlIEAAAAMBAJ&pg=PA52&lpg=PA...
Source: I helped develop CouchDB, but haven't really used Notes.
If two people were editing the same document in different replicas of the same database, then you would get two copies of the document with one labelled as a "replication or save conflict".