I mean, to be super candid back at you: if you don't have the bandwidth to maintain/support another open source project, I also doubt you have the bandwidth to maintain a custom-built key/token/password store entirely on your own, for free.

Your pitch for storing "API keys, tokens, and credentials" puts you personally in a rather liable position if someone uses this exactly as described, and you've made a mistake in code no one else has seen that either gives YOU those credentials, or leaks them somewhere another party can see them. (Analytics, logs)

For yourself, this is kick-ass and solves a real problem. But I might refrain from pitching it for use by others because there's basically only downside for you in that.