Hello,
We don’t have such practice in License Server which works like a cluster node.
But I think you don’t have to deploy a high availability server because your user’s PC doesn’t have to connect to License server every time.
Per this doc:
We have a time limit "CALs are valid for 60 days before renewal or 90 days before reassignment."
So, most of your users won't be affected.
And "RDS CALs can be overallocated", it means you can just deploy a server2, and configure it in your GPO too. When server1 is down, you will have an overused status in server2, then you have time to migrate your CAL to server2 or try to fix the issue in server1.
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