BNA the application does not enforce your license.
You can run the "License Usage Report" to see the number of devices managed by your BNA application server. You then confirm if you are under or over your license. If over then contact your sales rep about increasing your license.
As far as your server resources your performance will degrade if you do not have enough based on multiple factors including, number of devices, number of historical configurations, Size of your device configs.... etc... There are too many to list.