Quill 1.0 is a free, open source WYSIWYG editor built for the modern web. With its modular architecture and expressive API, it is completely customizable to fit any need.
I know it has been long in the making. From a developer perspective, the APIs are very powerful, including a smart way to capture text change, that would allow you to build a collaborative editor reasonably easy. Check out the guides, they are very well written, including the section how to clone Medium using Quill:
http://quilljs.com/guides/clonin...
Incredible! I have been looking for a better rich text editor that has an API over DOM. Was thinking about building my own after not been able to find one. Now I am looking and reading Quill's code only to be impressed and taken by the ability of what Quil has become.
ArtSquare