Hi,
No problem with the usb-dmx interface. OSC is a network protocol and is totally independent of the DMX output.
Look at the images below for the LightjamsPAD and Lightjams OSC config when the PAD is running on the same computer.
Edit: The image upload doesn't seem to work right now. Meanwhile, you need to select the 127.0.0.1 network adapter for the LightjamsPAD OSC output, port 9001. In Lightjams, go in the view/settings and in the OSC tab, make sure the 127.0.0.1 or the 0.0.0.0 (any network adapter) is selected for the input with the port 9001.