Really don't understand this hatred.
Mui was born on Commodore Amigas as an extension/enhancement to its operating system.
So what's the problem if it runs on Amiga Os4?
It runs, in an opensource-clone way in Aros, and I think it's a blessing the three camps share such a good framework!
Stuntz's idea was a great one, even after twenty years, and hyperion paid for it.
I own all three amigoid systems and it's a good thing to have a similar behaviour on all three platforms when you come to MUI.
You write once and use the same code (or very similar one) on three platforms. Great!