Every actor/celebrity (indeed, every person in theory) has a right to control what others do with his name, image, and likeness - this is what the law calls the "right of publicity."
So you can't just paste a photo or drawing of a famous person onto mugs, etc. and sell them for profit.
That is, apparently, unless that person is Bill Murray. He certainly could act to stop this but he hasn't.
I guess this fits with his eccentric-oddball persona. Very odd, legally speaking, but a nice way to relate to the people. Don't know the first thing about the man personally but this is the kind of thing that makes me want to know someone who can be so engagingly goofy.