Depends on the situation. I have to pick DS up from school if he wants to bring a friend home as the bus pass is specific to that bus, ie we live in village A, friend living in village B would only have a bus pass for bus for school to village B, would not be allowed on DS bus.
If it's a case of being in town and friend has not got money for bus fare, when it's been prearranged, I would say that it is friend's DP responsibility to go and get him.
At the end of the day it would probably depend on what mood I'm in!