I dont know anything about the Maxnc setup, but it looks like a simple stepper driven 4th.
The two wires in that plug "may" be a brake so it holds steady after stopping. Or it could be the main power for the driver to feed the stepper. Its got to get main motor power somewhere and its not going ot from the computor. The rest is going to be the stepper driver.
you will either have to find the wiring diagram to the driver box, or take it apart and figure it out.
It may be possible you simply didnt have the pins and such setup wrong in Mach to work with it, or it may have needed the brake released (if thats what it is). Or the Laptop may not even work with it, may need a desktop unless you know for sure that this laptop will run Mach thats very possible.
Either way it should be possible to run it through Mach & use it as a indexer.