Yeah, install MUI. It's not "required", but so many programs use it that you'll be quite limited in what you can run if you don't have it.
It's a little confusing - you want to install the
Picasso96 drivers,
not the Picasso II drivers, which are absolutely ancient and completely incompatible with just about everything.
EDIT: P96 drivers are probably also on the 3.9 CD, but I don't know how up to date they are.
EDIT2: Whoops, I see you you've already found P96 :-)
