I think the problem is that he's selling the maps as a service. A homeowner doing it for themself is different from hiring a professional service to do it.
If the Engineering Board (EB) wants to require formal stamps for their engineer's outputs, they should define that. They don't have the authority to regulate lumber, meat, the thickness of paper, or other markets. This market is separate from their standard market for engineering marks -- this is the market for approximate views from derived data with no legal standing for Engineering work. The EB wants to make that an established guild only. No consideration is needed IMO.
Colloquially, it means "I get paid money to do this thing."
Legally, it means "I am an accredited member of a guild that restricts access to my trade" - think doctors, lawyers, etc. If there's a board/bar type association that gives you permission to make your money, then you're a professional (legally speaking).
The problem in this case is that there are relevant professionals (surveyors/engineers) who are trying to protect their monopoly on…drawing lines on maps.
He shouldn't have let himself be quoted as a "professional tracing company." That's a load-bearing word in this context.
The other term is "amateur". That is not related to profit or renumeration.
Amateur does not mean unskilled. Amateur radio is full of highly skilled and expert people.... Who are forbidden from taking renumeration for radio services.
You can read the Wikipedia pages on professional and profession if you don't trust my memory. (One of my general ed classes was on the history of professions.)
The word "professional," as used by bodies like The California Board of Professional Engineers, strictly means someone who is board-certified to practice that profession. (There are a bunch of requirements to get that certification and become a professional, but the specifics aren't important here.) It has nothing to do with whether or not someone accepted money and everything to do with acquiring and maintaining the credentials legally required to enter a regulated line of work.
https://en.wikipedia.org/wiki/Professional https://en.wikipedia.org/wiki/Profession
How a body uses it isn't relevant, though. If I set up a body called The California Board of Jean Wearers and define "Jean Wearers" as people who wear Levi's, other brands are not obliged to rename their product.
Well, perhaps they would be in California. But that would be the same level of silly as this.
"Profession" and "professional" have precise legal meanings, which roughly equate to "the government gave us a monopoly on gatekeeping who is allowed to advertise themselves as one of us." That's the true meaning of those words. They've colloquially drifted over the years (through the use of phrases like "professional sports") to have a second meaning "people who get paid to do a thing."
The California Board of Professional Engineers is a professional board in the traditional sense of the word. The government gives that group the authority to decide who can be a Professional Engineer, including apparently who can say where the boundaries of a plot of land are.
There's a collision of definitions here. Since the whole case is on whether or not the professionals (in the first sense) can keep this guy from practicing, it's ill-advised for him to use the term "professional" in the second sense.
You can try to start the California Board of Jean Wearers if you want to. IDK if there are restrictions on who can call themselves a "board," but w/e. You certainly won't have a .ca.gov website (like the Board of Professional Engineers has), and you most certainly won't receive a monopoly from the government to define who can call themselves a jeans wearer (which the Board of Professional Engineers has).