You don’t need any permission from anyone to do anything with Slicer. Most extensions come with restriction-free license, so you can do anything with those, too.
I know that all TotalSegmentator models that you can run without obtaining a license file, all MONAI Auto3DSeg, and OpenAnatomy are all freely usable, without telling anything anyone.
SegmentWithSAM, Segmentantbone, MEDSAM may be a bit immature.
I don’t know what you mean by VolView.