Re: Windows VM?
Linux hypervisor and Windows guests is licensed per running instance of Windows.
Licensing is not my job so I may be inaccurate, but this'll be close enough to get you within reach:
Yes, the license is attached to the hardware. A Windows Server Standard license permits (from memory) the bare metal plus 2 VMs to be run (it may be simply 2 instances including the bare metal). If the bare-metal OS is not Windows, you get 2 VMs. The VMs are limited by the number of CPUs and cores as per the Windows Edition specs.
Windows Server Datacenter permits as many instances of Windows Server as you can cram into the hardware. Again, they don't care about the hypervisor. Since it's unlimited instances, many people just install Windows Server and enable Hyper-V. I think that's a little foolish because you can run a free hypervisor in a mixed Windows/Linux environment and keep some hardware Linux-only (and not pay for a license).
Service provider licensing is changing for Windows Server 2016 to a per-core model, where the license is prices that 8 cores is the same cost as one socket on 2012R2.
Again, licensing is not my bread and butter. Speak to a reseller and they'll keep you straight. In fact, speak to Microsoft - I've always found their licensing people to be very helpful and friendly (presumably because I'm actively engaging with them and trying to make sure we're always compliant).