Thats the definition of fishing in the first couple of pages of the regs.  Fairly straight forward to suggest that holding the rod and winding in a fish is very much the act of fishing.   

Much as the regs essentially cover it, I think you would have to come across a fairly hard line ranger that would issue an infringement to someone for being your net person, or spotting fish that didn't hold a current license.  Not to say that its not considered part of the act of catching a fish.

Realistically a license is cheap, so if someone is interested why not just get them to buy a day license to test the waters with you, and they can then decide if they want to give it a proper go and buy a season license? 

Oh and obviously this might be defined differently by the DOC license for those around Taupo.