Couldn't you also just setup an emacs server that listens over a TCP socket?

https://www.gnu.org/software/emacs/manual/html_node/emacs/TC...

Pointers?

Run and emacs server, and multiple simultaneous connections into it.

Is there a setup that lets multiple people edit at the same time?

Yes. It's not the sort of thing you'd use with untrusted parties over the internet since it requires access to the remote x-server, but it totally works for collaborative editing (esp with people sitting in the same room):

https://www.gnu.org/software/emacs/manual/html_node/emacs/Mu...