Thanks for that! I recommend anyone who wants to minimize risk to follow their instructions for self-hosting:

Is the source code available and can I run my own copy locally?

Yes! The source code is available on Github. Its a simple static HTML application and you can clone and run it by opening the index.html file in your browser. When run locally it should work when your computer is completely offline. The latest commits in the git repository are signed with my public code signing key.