Vaultwarden is a third-party implementation of Bitwarden‘s API. The upstream Bitwarden is a freemium password manager with multiple platforms supported. The feature differences can be found here. The Premium account only costs $10/year, which is definitely worth it.
If you care about your data security so much, you can host your own server with the official Bitwarden backend, which is resource-heavy. But vaultwarden is less resources-intensive and completely free. You do not need licensing from Bitwarden, and you hold your own data. However, vaultwarden does lack some features that the official Bitwarden backend has. For more information, check here.