Yes and the source (that I've looked at) is high quality. That said, it's a very complicated program with no room for mistakes, and it is written in C++ so plenty of opportunities for memory/pointer issues. RethinkDB is very stable these days, unlike a year ago, and I think it could work well as a full open source project at this point (given the good code quality and docs). Absolutely critical to that would be relicensing everything under a much more liberal license than AGPL!!