Where can one read the source code of setup.exe

That's, e.g., how I would determine what these commands do

I have had HN replies in the past that argued Windows is open source and thus comparable to UNIX-like OS projects where _the public_ can read the source code and make modifications, _for free_

Absent the source code, we can read Microsoft's documentation

https://learn.microsoft.com/en-us/windows-hardware/manufactu...

It seems like WinPE is the most useful version of Windows, e.g., it allows more options to setup.exe

How does one quickly and easily download and install a copy of WinPE, preferably on removable media