alternatively, donate to openbao the amount you'd pay for Vault support. you'll help ensure the project doesn't fall into disrepair and get more influence over fix/feature prioritization than you could with Vault.
If you're so inclined, please do!
We'd of course be appreciative of it, but that said, the OpenBao TSC had tabled conversations about just what we'd spend any funds on until after we moved into the OpenSSF... Which just concluded which means it might be time to get things moving again. But just to say, we may not immediately know what we'd spend any donations on. :-)
(Alternatively, hiring and retaining a maintainer or a firm working on it would also be good options. Part of the growth requirements of OpenSSF projects is to have more than a handful of companies on project leadership so increasing diversity is a key goal.)