I had the same concern. There's also the matter of supporting upstream development, which the maintainer does address in his readme. I ended up paying for a premium subscription of vanilla Bitwarden, which I self host. Sure it's overkill on resources and number of containers, but it's still insignificant. It seems slightly more safe to trust a company that depends on the software for revenue, if I'm going to use it without auditing the source. I've also e-mailed their support quite a few times, and they're great. It just doesn't feel right to me to do that while using a free custom backend to avoid the cost...