All ENTTEC DMX USB products only support one piece of software at a time; you cannot use one DMX USB interface to connect to multiple pieces of software.
OPEN DMX USB is an output only device.
DMX USB Pro has been designed to either receive or send a DMX stream at any one time, not both.
The DMX USB Pro’s input and output ports are physically connected to each other, therefore trying to recieve and send DMX streams would cause data degradation and flickering. Having the DMX IN and DMX OUT options it means that it can be integrated as part of a DMX chain when set to receive DMX data (in the same way you can daisy chain DMX in and out of a lighting fixture).
DMX USB Pro Mk2 features two independent DMX ports, meaning it supports two separate input and output universes concurrently from your lighting control software (providing your control software supports this). Similarly to the DMX USB Pro, the DMX USB Pro Mk2's Port 1 input and output are physically connected to each other, therefore trying to recieve and send DMX streams would cause data degradation and flickering. Having the DMX IN and DMX OUT options it means that it can be integrated as part of a DMX chain when set to receive DMX data (in the same way you can daisy chain DMX in and out of a lighting fixture).