To be honest, I didn't realize it was AGPL until they shut down (though I have to admit I haven't used it in any real project and thus haven't really evaluated it too deeply).
My understanding would have been that AGPL means all code that interfaces with the database (i.e. all code that uses ReQL) must also be AGPL. That would have instantly disqualified RethinkDB for me (whether the understanding is right or not) and I'm sure I'm not the only one to think that way.
Considering even GPL-licensed software often prominently advertises commercial dual-licensing, this seems like a major oversight (if it wasn't for ideological reasons).