Yes they are moveable. Depending on exactly which folders you move, you may need to re-specify the location. The instrument loading files (nki) use a relative path to the three one-gig monolith sample files (nkm). You can move the nkm's without touching the instrument definition files, but you will need to open the Options menu (if KP1) or the Info tab (if KP2) and specify the new location under "Library Installation Path."
Rescanning the plugins after the move is probably unnecessary, but wouldn't hurt if you experience problems.