nrlolsrd seems to be the Naval Research Laboratory’s separate implementation of olsr protocol (not a patch for existing version of olsr of ns2).
protolib seems to be a generic framework for easy development of protocols for ns2 and other platforms.
so I belive that, technicaly both of them can co exist in one instalation of ns2.
You may get the idea by exploring OLSR code.
Refer this link for installing OLSR in ns2.
http://www.projectguideline.com/modules.php?name=News&file=article&sid=15