The sharing machinery isn't open source, mostly because it's pretty tightly coupled to our community forums, which is a custom rails application.
I know that the jupyterhub team was working on https://github.com/jupyterhub/hubshare for a while as an open source sharing solution. I've also commented in https://github.com/jupyterhub/hubshare/issues/14 and elsewhere that I think PGContents (one of the libraries I talk about in the video) could be used as a basis for many kinds of sharing (though probably not realtime collaboration).
I know that the jupyterhub team was working on https://github.com/jupyterhub/hubshare for a while as an open source sharing solution. I've also commented in https://github.com/jupyterhub/hubshare/issues/14 and elsewhere that I think PGContents (one of the libraries I talk about in the video) could be used as a basis for many kinds of sharing (though probably not realtime collaboration).