The information that little snitch is not free, is however, not in the title, it even implies it is. Probably why they asked the question.

Yeah, I see that. My intention was "it's a macOS firewall (like little snitch)", not that it was "free and open source (like little snitch)". Apologies, but I can't edit the title anymore.

No worries. I didn't object to the title, so much as to the parent comment that suggested the original question was something that should have been obvious from the title, when it was not.