Mario Fuentes and I had decided to use GNOME Canvas instead of DiaCanvas#. Reasons? Same as before. Mario sent me one sample, it is based on the old Dia#-Clock, this is our first attempt to create UML#. You should be able (now) to get it from our CVS.
I'm also reading a very good/old book for UML called "UML y Patrones" I encourage to read it, very good book.
I learned today: 'MonoUML is not inactive anymore'