Embarrassed not to get this. It’s an editor not a builder… but there’s no mention of building a site elsewhere. I’m confused - I don’t think this is an overlay on another CMS but… wth?
Build your website using handcoding / Bootstrap / Foundation etc, and then ‘plug in’ Surreal CMS to allow clients to edit their content. Surreal is not a builder, it is just a Content Management System.
The beauty of Surreal is that it very simple for designers/developers to add to a site, and it is very simple for clients to use. Much simplier than Wordpress for example. And because it is a paid for service the support is great.