The OpenMUI initiative is a project that aims to opensource the MUI toolkit and port it to unix platforms. So far, MUI has already been ported to various architectures. Here’s a comment by Stefan Stuntz about the porting effort:
<stuntzi> where's my mountainbike?
Which is encouraging and shows that the project is on the right track.
Seriously: what was OpenMUI?
In 2008, I was looking to write an Ableton clone for Linux but was not satisfied with the existing UI toolkits (GTK 2 was a bad joke and Qt required KDE and C++) so I had a discussion with Stefan about doing an MUI port.
His conclusion was that MUI was too “amigaish” and it would be a real pain. There are many paradigms that don’t make sense on an unix platform (tag items, UI described as arrays instead of more modern things like XML, lack of skin system: nobody would want to configure every part of the UI anymore, lack of graphics abstraction: MUI is very low level, intuition dependencies, and many more…).
I agreed with him and then moved on to other stuff. It is true that MUI was a revolution back in its time but it is not portable. Nowadays I’m mostly satisfied with JavaFX.