Carbon Emacs acts like emacsclient or gnuserv by itself, i.e. it only runs one instance and opens files in this instance from Finder automatically.

A drawback of this behaviour is that the usual server-window variable of gnuserv has no effect. When using elscreen to get tabs into Emacs the desired behaviour might be to open a new tab in the running Emacs when you open a file from Finder. This can easily be done, using my intelligent-kill command (see my elscreen posting) such that files from Finder are opened in a new tab, and you can close this tab with the usual C-x C-c: