Hi Jon.
I would advice to talk to Microsoft about this, VMware is not in the position to advice in licensing needs and terms for another software.
Microsoft have published a document to try to clarify this: http://download.microsoft.com/download/1/1/4/114A45DD-A1F7-4910-81FD-6CAF401077D0/Microsoft%20VDI%20and%20VDA%20FAQ%20v3…
One note however, the licensing should be the same no matter on what VDI solution you are using, so the same terms no matter if you are using Microsofts, Citrix or VMwares solution.