If so, you can check out Infisical (https://github.com/Infisical/infisical) as an open source alternative to Vault. The absolute majority of our codebase is licensed under MIT and we have no intentions to change that.
I'll definitely check it out. That said, I'm starting to feel a lot more skeptical of the ability for even founders to manage stuff like this. I would say the same of my own OSS as a "founder," but if my company controls it in some way then I'm not sure there's a reasonable way for me to ensure that continues in perpetuity. At least not via a split model like a lot of these recent news stories have revolved around.
From what I've seen of Mitchell as well, at least in the past, I kind of doubt this is something he would have gone through with on his own.
I think the easiest way to manage it is essentially to do nothing. Accept open source contributions without a contributor license agreement and their copyright locks in future maintainers, yourself included. Extricating those contributions eventually becomes impossible without a cleanroom rewrite that is usually economically impractical and way too risky to a business with revenue.
This requires a copyleft license, and can be bypassed if all contributors agree to sign away their code to a company trying to relicense and monetize the code (as the Audacity contributors did for some reason).
Disclaimer: I'm one of the founders.