Checks before first run of VFD

[JAZZCNC]

You don't happen to have any info/manual for this unit do you?

No sorry it went with the machine when sold.

If I wanted to run it with a relay, is it a case of shorting FWD to GND? To stop it, opening that short?

Yes exactly like that. Often your BOB will have relay output on it for this purpose.

To control the speed, with a pot or software, is it a case of feeding in 0-10V to the '10V IN' (referenced to the GND of course)
For a pot, can I use the '10V out' for a voltage divider?

Yes but don't use Gnd. The Analog Speed control is isolated from the inputs and Gnd is tied to these inputs.
Use like this for POT.
10V (OUT) to leg #1
10V (IN) = leg #2
0V = Leg #3 .

If using Speed Reference from external source ie: Via software control then just use 0V & 10V (IN)