Disney’s Magical Express is a shared ride. It is not meant to be specific to a single resort. Of course, if enough people happen to be going to that one resort all at the same time, I’m sure they’d plan a bus to accommodate that.
Your friend will need to be named on your resort reservation AND must have a specific Disney’s Magical Express reservation in his name, or else he will not be permitted to board a DME bus. DME is free, but only for registered resort guests, and only with a DME reservation