Actually, here is the relevant info:
Which VIs are Installed with NI-IMAQ and Vision Acquisition Software?
and this:
Is a License Needed to Work With NI Vision Acquisition Software?
So it looks like nothing additional is needed for the computer on which the IMAQ hardware is installed (or from which it is run), but officially, any other computer (including a development computer) would.
If your client is not using any IMAQ hardware, they are not supposed to use code (development or runtime) that uses these VIs.
But again, I may have this all wrong, although that is what I remember from the time we were using an IMAQ frame grabber.