Virtualization and software licenses?

Question

Virtualization

Often, when they ask for advice on the Internet on how to assemble a particular service or a group of them, they advise doing this: each service should spin in its own virtual machine, for example AD + DNS + DHCP in one, a terminal server in another, but for example wsus - in a separate virtual machine.
Now the question is: where can I get licenses for wndows server for all this economy? Are they bought for each task, or are there some workarounds, and I just don't understand MS licensing policies?

Answer 1

One Windows Server 2012 R2 Standard license is enough for 2 virtual machines running on the same server. Windows Server 2012 R2 Datacenter for an unlimited number of VMs on a single server.
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Answer 2

Bought for every car. There is a trial for tests.

Answer 3

if the company does not have open source money in your hands)