The framing of the title is a bit disingenuous. He is not “talking” about engineering to a bunch of college students. He is providing expert opinion in a court case. This is a whole different deal and I think there is nuance here. Honestly, I don’t like the manipulation with the title and how they are framing the whole thing. Makes me cautious about emitting an opinion.
Engineering licensure is generally opt-in for activities that require it, and you obviously don't need to be a licensed engineer to testify plainly in court (contrast with signing off on plans for a building, for which you do), so he should be in the clear.
Of course getting this close to what the state board considers their turf (Professional Engineer expert witnesses, whose testimony carries more weight) explains why they're trying to stomp on him - similar to that engineer in Oregon who got legally harassed for a bunch of years for doing math about red light cameras.