What's the difference and version of VRPN and VRUI within ParaView-VR

Dear SIr or MS:
The developement of both VRPN and VRUI is pushing quickly. So I want to know what is the difference of VRPN and VRUI used in ParaView? When I use VRUI plugin to compile ParaView, there’s always errors, but VRPN, no problem!
Could you please tell me the used version of VRPN and VRUI in the different version of ParaView, especially version 5.8.1 ParaView?