Rory,
as far as I know, TServer checks out license AT STARTUP ONLY. That is, it will check out ALL THE LICENSE you have allocated it. In other words, if your option of numoflicense = 0, it will get ALL the license. If your numoflicense is 70, it will get 70 licenses.
Then, it will start registering all your DNs. If you will have more than 70 DNs, it will fail to register all the DNs after the first 70. So, in theory you will have to buy MAXIMUM number of seats you expect ot use, even though you only use half of them.
However, Genesys is a very smart company. I was told by my counterpart in U.S. that they know that most of the customers WILL GROW. Thus, there is a very interesting functionality included with TServer. Since numoflicense supports dynamic changes, you can modify numoflines to a number you want AFTER TServer has been started. Then, you can add DNs for additional agents.
Needless to say, Genesys does not support this type of operation, plus YOU MUST BUY the additional licenses from Genesys if you plan to continue to use it officially.
This hack might work for really emergency situations; however, in most cases, Genesys is very flexible and would usually issue you a temporary license almost immediately should you ever experience this kind of situation.
Also, DO NOT SHUTDOWN LICENSE MANAGER UNLESS YOU WANT YOUR TSERVER TO SHUTDOWN. Shutting down license manager AFTER starting TServer WILL shut your TServer down almost immediately.