And quite likely more expensive than the spurious license fee. Lawyers and businesspeople might pay them to go away, it takes a (self-proclaimed) nerd scorned to go for justice here!

I very much doubt it would be more expensive, even for whatever the going rate is for a spray-and-pray license scheme. In a half hour phone call, a decent lawyer can learn the facts and assess this fact pattern and say “this is a fishing expedition, don’t respond, call me back when they send a demand letter (they won’t) or file a lawsuit (they won’t do that either).”

Never pay scammers, they rely on your calculus and once they know you pay, just like bullies, they will keep coming back for more blood until you run dry.