Until last year and for two years I kept an Etherpad Lite to do shared text editing and it was amazing. It was in use for three years. The only reason I stopped using it was Google Docs, who bought the company or IP for Etherpad, can do the same thing and therefore I don't have to do the Linux maintenance. I even had it use SQlite as the database and it could handle as many as 30 simultaneous users without a hitch.

Etherpad Lite (https://github.com/ether/etherpad-lite) is a port to javascript, is backed by the Free Software Conservancy and is not owned by any corporation.

Yes, if you do not mind using Google's infrastructure, Google Docs is easier & more featureul. There are some cases in which running on premises may make a difference, and Etherpad strives to fill that palce.