My rear driver side caliper has been out apparently for a while.. The rotor is rusted over so its been seized open.. Is there anything else on the rear brake system that code cause this? Or is the caliper the only piece..

 

The rear calipers are the usual suspect, other than that it could be a crushed brake line.

 

could also be the slides are stuck. But you would still need a caliper if thats the case =P