See below for the SWD restrictions on licensing. Basically, if you delivered any software package to a client, it will consume a license. As Dominque pointed out, you may have a unique situation, and if you are close to a licensing threshold, it may be worth calling support to clear up.
Software Delivery Solution for Windows
* License consumptionA license is consumed the first time a managed computer requests a software delivery task. The prerequisites for this event would be the assignment (via the Notification Server console) of a software delivery task to a managed node that has the Software Delivery Solution agent installed. A license is not consumed from the existence of the Software Delivery Solution agent and/or the Task Synchronization agent on a managed computer.
* License count exceededAll agents that attempt to obtain Software Delivery Tasks beyond the allowed node count will stop receiving the task details in their client policy files.
* License expiration (only applicable to Trial or otherwise temporary licenses)Agent rollouts will still occur without a problem. Software Delivery jobs will be no longer be advertised to clients, including newer schedules for existing tasks.
* AUP expirationAll functions will continue normally. However, if newer versions of the solution are installed, they will not function.
* License recoveryRetired computers will not release a license.
o Computers can be deleted to release a license
o For unmanaged computers, the event deletion in Data Purging for Software Delivery can be used to clear out old records and free up licenses. This will not work for systems actively using Software Delivery Solution.