I am not only a pilot, I’m also familiar with flying Wisconsin.
A couple of points, as someone who has flown in Wisconsin, flown a Stearman (although not nearly as many hours as the pilot in the article), and someone who routinely flies at low altitudes:
Regarding rivers as “congested areas” - in Wisconsin, rivers and lakes are often commercialized and full of tourists and related industries. As a result, you can have a LOT of people on a river or lake. This has been an issue in the past with pilots flying at low level even when no accident has occurred. Many of us who fly in Wisconsin thus treat rivers/lakes much as we treat subdivisions - we fly higher over them than over “uncongested” areas. Typically, I flew 1,000-2,000 feet above everything in Wisconsin, regardless of what I was flying, unless I had a very specific purpose in mind in a very specific location which I would double-check for safety. Even in ultralights, which are intended for low altitudes and which are typically flown at 500 feet, when we flew them transiting from one area to another we usually were 1,000 feet or higher above ground. Why? Well, powerlines were high on the list. So yes, arguably, he was flying lower than he should for the conditions at that time at that location. Saying “but I thought I was further down the river” doesn’t cut it - you are supposed to know where you are at ALL times.
Stearmans have shitty views forward. Really. While tailwheel airplanes are noted for poor forward visibility on the ground the Stearman’s situation doesn’t improve much at altitude. That means they require extra vigilance while navigating. If you can’t manage that you shouldn’t be flying one.
Powerlines are notoriously hard to see while in flight. This is one reason that heavy concentrations of such are marked on air navigation maps. Not to mention they’re dangerous and collisions with them are frequently fatal. It is the pilot’s responsibility to avoid powerlines.
OK, with the two above points - why is someone in an airplane with poor forward visibility flying below powerline height? That, to me, is where negligence enters into the picture. Is it legal to fly a Stearman at a lower height than powerlines? Yup. It’s also legal to ride a motorcycle in my state (Indiana) without a helmet. That doesn’t mean it’s a good idea, or isn’t more hazardous than the possible alternatives (higher for the airplane, helmet for the bike).
In other words, yeah, I think he was in some ways negligent for this accident. All he needed was another 100 or 200 feet of altitude (which his passenger would never have noticed in regards to the quality of her experience) and there would have been no accident. I don’t think it’s felony-level negligence, but fatal car accidents wind up with those sorts of charges, too.
About the “commercial pilot” aspect - it’s not just a matter of dollars and cents, it’s also perception. Although I have split costs pro rata at times we were always very careful about how we did this. If there was a perception amongst strangers he was giving rides that he was, in some way, a commercial pilot that could be sufficient to trigger a violation. This is one reason (among several) why many pilots hesitate to give rides to strangers. When I give rides to people I don’t know well I am very careful to emphasize that I am NOT a commercially licensed pilot and tell them that if they have any hesitation about that fact I would be happy to direct them to a commercial operation. Confusion certainly can occur when the general public steps into a small airport situation (as an example, one of my old instructors would frequently ask me about regs, which I at one point was infamous for being able to quote chapter and verse, as well as weather conditions, which led to more than one tourist asking why a professional pilot was consulting an amateur, usually explained by an analogy to driving in that one can be a very competent driver without ever getting a chauffeur’s license, and he who was last on the road is most familiar with conditions there). Personally, if it’s a stranger I accept NO money whatsover. Nada. None. Anyone insisting I accept money over my objections will not get a ride simply because I do not wnat to risk my license due to a misunderstanding.
From my viewpoint, this is on par with picking up a stranger and giving them a ride in your car, then getting in an accident after you blow through a stop sign. Yes, there is some negligence. My position is that the passenger also assumed some risk here (most people do not need to be told that there is an inherent risk in flying). Some penalty for the pilot, who was responsible for a flight that ended in a passenger death, is called for although I do not like to see this labeled as criminal. There was certainly no malice involved, it was just a dumb accident resulting from a moment of inattention of the sort to which we are ALL prone.