RAGBRAI is of course a registered trademark. pilderwasser is not a county in Iowa. the images you see may or may not be silkscreened on t-shirts. I am without sufficient information and can neither confirm nor deny any allegations at this time.
If they were silkscreened (I'm just saying), I bet they would get good circulation over here on the right coast.
PS I thought Grinnell was in Pilderwasser county. At least it should be.