Is there any way to use Emacs for collaborative editing, while there is at least one person who doesn’t use emacs, but rather some popular IDE? It should also be possible to edit multiple files at the same time.
Other solutions seem to expect all people to be using Emacs.
Use a git repository for collaboration.
Or do you mean real-time? (there were a few intents for that, time ago…).
Yes, real-time for online peer-programming.