There are many free etherpad implementations since it went open source. Does etherpad support syntax highlighting or is some kind of add-on available?
I tried http://typewith.me/ http://sync.in/ http://www.piratenpad.de/
You can install a plugin in Etherpad called "Syntax highlighting".
To install the plugin simple visit /admin/plugins on your Etherpad deployment and then search for "syntax" and click Install.
For details on the plugin see https://npmjs.org/package/ep_syntaxhighlighting