MUI4 here is a "backport" of MUI4 for OS4, which is a reimplementation of MUI4, as found in MorphOS, for OS4. I don't know how much code is shared between this MUI4 and MUI4 in MorphOS, but they are certainly not 100% compatible, and as time goes and they develop each in their own direction, who knows how it will end up. And then there is Zune. It is truly a messy situation with all these randomly compatible incarnations of MUI.
