Hi,
1.RDS Cal will only be used when several users would like to remoting to the VDI pool with RDS deployment at the same time.
2.According to "Licensing the Windows Desktop for VDI Environments " PDF, it mentioned two types of licensing provided for windows deskotop of virtual environment.
How does Microsoft license the Windows® desktop for virtual environments?
Microsoft licenses Windows for virtual desktops by access device:
• Virtual desktop access rights are a benefit of Windows Client Software Assurance (SA). Customers who intend to use PCs covered under SA have access to their Virtual Desktop Infrastructure (VDI) desktops at no additional charge.
• Customers who want to use devices that do not qualify for Windows Client SA, such as thin clients, will need to license those devices with Windows Virtual Desktop Access (VDA) in order to access a Windows VDI desktop. Windows VDA is also applicable to third party devices, such as contractor or employee-owned PCs.
Link: /api/attachments/12620-microsoft-vdi-and-vda-faq-v3-0.pdf?platform=QnA
3.Last but not least, for questions related to the windows license, you could get a call support from VLSC for more details.
VLSC contact:
https://www.microsoft.com/Licensing/servicecenter/Help/Contact.aspx
Hope this helps and please help to accept as Answer if the response is useful.
Thanks,
Jenny