This is super cool. The idea of this project is that your whole app - front-end, backend, data store, everything is just a single HTML file. You edit the file (either through js tooling that this project provides, or in any other way - even DOM editor in your browser's developer tools). And it monitors DOM changes and uploads the new HTML file to the server, where it's stored as static HTML.
So you have a blog, you edit the HTML in the browser and then it's uploaded to the backend.
Or you have a kanban board, anything really. Don't like color of something? Fire DOM tools, change the colors, play with it and the whole app changes. HTML uploads to server. It has basic auth, which basically says who can edit and who can only view.
Very refreshing idea.