As you correctly guessed, the license_* web service operations are meaningful only for the Novell Teaming.

If your goal is to get the (approximate) number of users in the system, a workaround would be to call profile_getUsers() operation with firstRecord value being 0 and maxRecords being 1. Then, on the returned object, examine the value of "total" field, which should represent the total number of users in the system.