Are you sure?
Quite sure, yes
Are commercial software developers no longer required to pay an arbitrary registration fee to use and redistribute MUI?
I'm fairly sure they're not. Why not ask Stefan himself (quoting the same document: "Just contact me and ask."), he's quite reachable guy (when he's not mountainbiking around the world, see
http://www.alpenzorro.de/).
Reading between the lines, Stefan's goal was to create a new user interface standard that allowed him to share in the profits of all future Amiga-based commercial software offerings. (Actually, I'm just paraphrasing the text at http://www.sasg.com/mui/policies.html and not really reading between the lines.)
That document is very very old.
If registrations and contract negotiations for commercial software developers are no longer possible for some reason, then no one can create commercial software using MUI, regardless of how the end user obtains the MUI user archive. :-/
"Just contact me and ask."
I'm just being grumpy. :-) As a user, I never liked how many third party widgets I had to install to get a mostly functional Amiga system up and running. As a developer, I try to stick to what a vanilla operating system installation provides.
MUI comes as a standard component in various OSes.
