The plugin is built on top of Y.js which has CodeMirror integration out of the box, so the code is very simple especially for such a complicated feature.
Now, this is only a prototype and lacks many functions. I expect that implementing collaboration properly might require changes in Joplin core as well.
Plus it's not obvious to me how to handle attachments and note links.
P.S. Even plugins like quick links work!
I was intrigued by the title, but this first post didn't help me understand what's the plugin exactly about and how it works, care to explain a bit?
This was more of a prototype so I did not write a very detailed explanation but basically this plugin allows 2 Joplin users together edit a single note. On my video it's 2 copies of Joplin side by side but it can just as well be 2 different computers.
Now, this is not a complete solution, and I probably won't do any more work on this. In part because there's a similar GSoC project but mainly because I do not need this function.
Thank for the info 
Is the prototype available anywhere?
I might have the need for at least read only access to my notes, but without using my dropbox credentials, so this one looked promising but I couldn't dig up anything more than this post...
I don't think I have published it and it won't be useful for your purpose.
Instead check out these posts, I think you might find them relevant:
Thanks, I'll look into it.
