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).”