"if one uses another's work as visual reference"

That is kind of vague wording in an already grey area. Like looking at the edge flow of a cartoon style girl for ideas of how to approach modeling a totally different cartoon girl that you're working on probably won't raise any eyebrows but if it turns out you're basically recreating that character and calling it your own work well...that's another deal altogether. Whether confirmed or not, no one wants their name caught up in that.

In the end, I have to agree with NextDesign.