How "open source" is Bitwarden? From what I can tell (https://bitwarden.com/pricing/), the client is open-source, but the service feature-gates a large number of features behind premium accounts. Is this feature-gating accomplished by the server or the client? Is Bitwarden truly community-owned free open-source software, or solely a complement to their commercial services and open-source to make for better marketing?

There is an open-source server called Vaultwarden, but it is unofficial. The only truly open source part of Bitwarden is the client. :(

I hadn't realised half the "official" server was under a non-commercial custom licence. https://github.com/bitwarden/server

Last I looked, it wasn't fun to self-host anyway. Vaultwarden ftw!