Help is needed !
I continue work on the system and the problem reduces to this:
If I have NI Vision 8.5 deactivated (unlicensed), but NI Vision Runtime 8.5 active (licensed), I get a "Unlicensed copy of NI Vision" error for at least the following VIs:
* IMAQ Fill Image
* IMAQ Draw
* IMAQ SetColorPixelLine
Most other VIs work, however, so I know I have a valid Runtime license. Presumably there are others with this problem as well, my search was not exhaustive.
If I then license NI Vision, all those errors go away. So it appears that the Vision Runtime license (at least on my installations) doesn't comprehensively cover all the VIs available with NI Vision.