As far as I know, you used to get one free license based on the serial number of the card. Their website says:
Note: If you have purchased a Dante product that entitles you to a free or discounted copy of Dante Virtual Soundcard, details of how to obtain this will be provided in the documentation accompanying your product.
As Scott mentioned, some of the older A&H Dante cards (I believe for iLive) did include a DVS license (hence why the website says, “IF you have purchased a Dante product that entitles you to a free DVS copy…..”
I can confirm from personal experience however that the current generation of DLive/Avantis Dante cards do NOT include a DVS license.