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.

Thought "isn't that just Wine" but no! They are virtualizing it! And integrating them seamlessly with Linux desktop somehow!

Looks pretty cool. I remember playing with something similar in Virtualbox, it had a seamless mode too. It was a bit janky, and I think they removed it recently.

I used it in the old days, to have MSN messenger on Ubuntu :)

Ok. Can you run WSL inside of it?