Licensing VMs with Linux is actually the simplest scenario for Hyper-V. So far, you've seen that, from the licensing perspective, if you have a Windows Server VM, all you have to do is to associate the correct number of Windows Server licenses according to the number of VMs and processors on the host.

If you're running only Linux VMs, you actually don't need any license from Microsoft. The most obvious option is to use the Hyper-V Server that requires no Windows Server licenses.

Let's see an example: you have two virtualization hosts. Host 01 will run four Windows Server VMs and Host 02 will run 04 Linux VMs. Both hosts have four processors. In this case, you will need only two Windows Server licenses for the whole environment, and you will associate these licenses with Host 01 where the Windows Server VMs are. There is a caveat here, however: if you move any Windows Server VM from Host 01 to Host 02, you will have to license Host 02 as well. This is not true...