A service is represented by a path namespace (without a leading "/") and is registered under /dev/name/global or /dev/name/local, depending on how it attaches itself. Every machine running a gns client or server on the same network has the same view of the /dev/name/global namespace. Each machine has its own local namespace /dev/name/local that reflects its own local services.
Here's an example after a service called printer has attached itself globally:
$ ls -l /dev/name/global/ total 2 dr-xr-xr-x 0 root techies 1 Feb 06 16:20 net dr-xr-xr-x 0 root techies 1 Feb 06 16:21 printer