Hi DC Ross,
I also have a JCut 6090B router with JNC-40M. I ordered my machine to run with Mach3. The machine is functioning OK, but you need to create your own machine as ArtSoft suggests. Mine came with an already configured Mill, however the screen is in Chinese. What I've done is, I screen captured every config screen the way they did the configurations, than I created my own Mill, and just set everything up as they did it. You'll have to fine tune the motors (Config-Motor tuning), it was a bit scary when used for the first time the "Home all axes", but that worked too. You'll have to set up the "Soft Limits" also. I only have one problem now, how to wire in the water pump to start when the spindle starts.
Good luck, Mike