Basically you just mark out some <div> tags as class="sc-content", and they'll become drag&drop WYSIWYG editable. The changes get written right back into the file, so you don't need anything other than PHP 5.4 and write permissions. You can even remove the SiteCake file again, and your site will just keep working (as static HTML).

Amazing, thanks for this. This is one of the rare cases when PHP as a language shines for a use-case like this.