The barbs on the M&B spear model are turned back. Their only possible function would be to make the spear impossible to remove from a wound. This would obviously not be a good idea, if the polearm was an infantryman's primary weapon. The Roman pilum used this sort of thing, but it was a deliberately disposable weapon - it was either thrown or driven into an opponent's body or shield and then released, to allow the size and weight of the weapon to incapacitate the target. The pictured weapon was clearly not designed with that concept in mind, so the barbs are, in a word, incorrect. The design was planned to look scary, not to actually work.
I don't even know which download you got. No, it is not, in its current form, functional with any other mod that modifies the item list at all. This package was purely intended as a resource for modders wishing to incorporate the RCM into their own projects. It is not really "playable" in current form.It sounds like you tried to add it over some other mod. No chance that will work.