AGPL is real show-stopper for serious adoption, IMO.
RethinkDB's drivers are Apache or MIT (I can't remember which).
Licensing the server as GPL/AGPL while making drivers Apache/MIT is an accepted practice in the database world as it provides the DB vendor with opportunities to protect revenue while the driver licenses protect developers from the GPL/AGPL.
There are plenty of non-AGPL DBs out there doing pretty well. Here are some examples of GPL/MIT/BSD style licensed DBs: Riak, Cassandra, Redis, MySQL, PostgreSQL, ArangoDB, CouchDB.
Many companies have dumb policies. They are the ones that need to change.