It depends on what you are installing on the slave server. If you have installed all applications on the master (CS, RME, CM, DFM) then you will need an additional license for the slave.
If you have just installed something like CS and RME on the master, and then CS and CM on the slave it would not require an additional license.
The key is that if you install RME, CM, or DFM more than once you will need additional licenses.
