> And hoping it includes all the java it needs, and doesn't go out and pick up some 3rd party library?

What Java? It's a self-contained, monolithic HTML file with JS and CSS inline. What dependency are you imagining you're not going to have?

> You would have to audit it to ensure it never includes everything else, or posts anything externally with every release.

Exactly as you would with KeePass, or any other conceivable solution. If you don't want to audit future releases, save the last one you audited and use that.