> Dates are just rough guestimates.

Just to put some of them right:

> - laire got the MUI3.8 sources sometime in 2001 and ported them to PPC
> - this was released as MUI3.9 for MorphOS0.4 and went back into Stuntzi's SVN/CVS/?

This was in 2000 and for MorphOS 0.2.

http://www.amiga-news.de/en/news/AN-2000-05-00060-EN.html
http://www.amiga-news.de/en/news/AN-2000-10-00364-EN.html

> - ca 2012 some OS4 contributors started retrofitting MUI4.x features into the MUI3.9 source tree

This happened earlier:

"Thore at tboeckel @ gmx . de, man who works 3 long years to make MUI4 and a bunch of related classes from scratch to OS4."
http://amigaworld.net/modules/news/article.php?storyid=6971