You have to keep the numbers of physical processore in mind when licensing Windows Server 2012.
- This License is for two processors
- You can use it for two virtual machines
- Beside this same functionality as Datacenter Edition
You can use Datacenter Edtion for a unlimited number of virtual machines.
CALs are still neccessary. Device or User CAL as in former versions are available.
- Choose Device CAL if several users are working on one device
- Choose User CAL if one user acesses a server with several devices
You can’t use CALs from former versions of Windows Server 2012.
- For more information and licensing scenarios in a virtual environment, read this e-book
- Guidelines on building a host with windows server (including samples)