You could do similar things to what FOSS provides using reverse engineering with proprietary software. For instance making a modified version of MS Windows and putting it up on BitTorrent or selling it in a store for profit. But you chance getting caught and sued or worse. The Windows EULA does not permit you to redistribute or modify Windows, even for non-commercial purposes.

Most companies and most users for that matter have absolutely no desire to modify their Windows installation either.

The fetish of wanting to brand, tinker-with, modify, swap-out and play with bits of software is something that belongs exclusively to developers.

A developer might say "Oh, curses, this software doesn't work in precisely the configuration I want. Right. Here's my Visual Studio, where do I prod".

A normal user - never mind one with actual work to do - says "Stupid software. Why won't you just let me do my work. Who do I have to telephone to get this software to get out of my face and let me do some work today?".