Have you copied Windows and tried to run it? I would love to see the plain text source code that you claim to have. We all would.
If we are talking about distillation vs building from scratch, none of these are congruent to Windows. I can build my own LLM [0] and then distill off of Claude, but that is not the same as a 1:1 copy of an operating system because there was the ability to crack how licensing works. We are not seeing Windows clones, at the source level, for that reason.
Also, Linux exists. Anyone can copy that. Why doesn't that count?