An addition to this blog post
Of course I had forgotten the semantics in the meantime, and google did not point me to my own blog. So with this entry I hope it will. Since one thing is for sure: I will need the screen command again, and it will also have forgotten how to use it.
In order to share one terminal session by two people on the same machine personA runs:
screen -S someName
the second person should be able to share the session by running:
screen -x someName