How do we implement licensing for Microsoft Office 365 in a Virtual Desktop Infrastructure (VDI)?
Microsoft Office 365 can only be set up in a Virtual Desktop Infrastructure (VDI) with one of the following editions:
– Office 365 ProPlus
– Office 365 Enterprise E3
– Office 365 Enterprise E5
Each virtual desktop which runs an Office 365 requires a license. This can be covered by using one of the five installations per Office 365 user subscription license. Moreover, each access on the VDI requires a Remote Desktop Services CAL as well as a Windows Server CAL.

Sources:
official Microsoft Technet Website on Office 365 Feature Availability (https://technet.microsoft.com/en-us/library/office-applications-service-description.aspx), retrieved 2018-08-21
Microsoft Product Terms, August 2018
Volume Licensing Brief_Microsoft_Office 365 ProPlus_as is 2018-08-21