[lavezza]

As others have pointed out, those official MS VMs are for evaluation only. You are not legally allowed to use them for development. Of course, you could pay MS for a license and do your Windows development in a VM on Linux (or Mac), so that is something that MS supports that Apple doesn't. But to develop for Windows or Mac/iOS you will most likely need to give some money to MS or Apple.

[AegirLeet]

This was non-commercial and there wasn't any development involved. Even if doing this in a Windows VM technically violated some license, I wouldn't care much for something that's just a hobby project.

As you pointed out, with Windows there's at least no technical barrier to running it in the VM. Even if I had to buy a license, that would be like a hundred times cheaper than buying a Mac.