Jure, PubSweet lead dev, found this very interesting editor built with ProseMirror and built by Atlassian:
It looks pretty good. The table editor in particular, while perhaps needing some UX love, is pretty awesome.
It is part of the Atlaskit, which is a psuedo open source design kit Atlassian released. I haven’t looked at it closely but large chunks, namely the styles, is closed source (see their styles license) but the rest uses the Apache licence. Their repo is here.
Also interesting is this blog post about their design process. Finally a project (albeit fringe open source) that talks about design workflow. Very interesting… I don’t like the ‘developerificiation’ of design (eg calling the process ‘DesignOps’) but I do like to see a project talking about design workflow. Awesome.