Slava @ RethinkDB here. I am not able to get into details yet, but the short version is that the commercial entity behind RethinkDB is shutting down. We're working on continuity for the open-source project. Full announcement (and details) coming in a day or two.
I chose RethinkDB for a core component of a project back in 2013 and really liked it. I think we were probably one of the earliest production adopters but sadly we couldn't talk about it much. I wanted a document store done right and RethinkDB was definitely it.
I hope the OSS project is able to gather steam.
Best of luck Slava.