See the Altiris licensing technical FAQ here:
https://kb.altiris.com/article.asp?article=16789&p=1

From the KB:

Inventory Solution for Windows

• License consumption—A license is consumed after the Notification Server has received the first posted software inventory data from a managed computer. A license is not consumed from the existence of the inventory solution agent on a managed computer. A license is not consumed by the "basic inventory" function of the Altiris Agent.
• License count exceeded—Inventory from licensed nodes will continue to be processed. Incoming inventory data from unlicensed nodes is discarded.
• License expiration (only applicable to Trial or otherwise temporary licenses)—Agent rollouts will still occur without a problem. All new incoming inventory data is discarded. Inventory reports will throw a license error.
• AUP expiration—All functions will continue normally. However, if newer versions of the solution are installed, they will not function.
• License recovery—As of Inventory Solution 6.1 SP2, setting the status of the computer to anything but Active will release a license.  In prior versions, only Retired, Return to Lessor, and Disposed computers will free up a license. Deletion of the computer resource record will also release a license.
  NOTE:  Inventory Solution specific data on Retired, Return to Lessor and Disposed computers will be purged as part of a background process that runs each night.

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