No, the license server is not directly connected to the Active Directory (AD). It only accesses the AD during the activation process in order to import users from there.
Since ThinPrint version 13, it is possible to trigger a synchronization with the AD via the web-based management console. This releases licenses for users who have been removed from the AD or deactivated there, provided that the 28-day blocking period has expired since the initial access.
If the 28 days have not yet expired, the license remains blocked for the remaining period.
AD synchronization is also possible with PowerShell.