honestly I wouldn't try to pull it out if it's really stuck until you are ready to replace it (yes I understand you need to get the size so you can order a new one) but you might damage something and not be able to ride it for a while. I would tell him he needs a new one and when he has the downtime to tear it apart to replace it, then do it.
I would try some penetrating lubricant (PB Blaster etc.) soak it overnight. You could also try tapping on a block of wood on the spindle (as if trying to knock the BB through the shell) just hard enough to try and break the bond between the threads.