To add onto this, if you care about supply chain attacks, bitwarden mobile supports Fdroid builds (albeit not part of the main repo because they rely on xamarin) so you can host your own fdroid repo and run your own builds if so desired.
I think they meant if they don't like the direction that the Android client takes, i.e. they stop allowing you to change the backend url for example in which case, yes you would need to fork or rewrite it
It's fragile if you do that. Bitwarden updated their API last month on the clients so you couldn't connect to Vaultwarden at all until the Vaultwarden team could reverse engineer the change and produce a new release.
