My understanding has always been that if a User has a CAL, and the user is using the same AD account to connect to multiple Orgs (eg Dev, UAT, Live), then they do not need additional CALs for the additional Orgs.
Whether the Orgs are on the same server or saame deployment (multi-tenant) or even a completely different deployment is not important.
If you do use multiple servers for the same or different deployments, you need a server licence for each one.
Hope this helps.
Adam Vero, Microsoft Certified Trainer | Microsoft Community Contributor 2011
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