This system works by launching an official Windows image in Docker and then making an RDP connection to it. There are a couple of others too now like WinBoat
What all of them avoid mentioning is that the images were intended by Microsoft for test and development purposes on Windows and the license clearly states you need a valid Windows license to use them: https://hub.docker.com/r/microsoft/windows#license
I wonder if Microsoft will take some action to enforce this if these projects become popular.
Edit: This comment is incorrect, see below comment from doctorpangloss
Most laptops have included Windows 10 or 11 licenses, which are valid for this use
I don't get it. Is it a VM in a container? Skimming https://hub.docker.com/r/microsoft/windows I would have interpreted that as a native Windows container, which I vaguely recall being a thing, but that would require an NT host, not Linux.
no, this system does not work by launching the windows containers on windows mcr.microsoft.com/windows images
it works by using dockurr, which is a great project but a worse way to distribute windows in the sense that it gets installed instead of downloaded and executed
https://get.activated.win wouldn't be online if microsoft cared.