You cannot disagree about facts. "Open source" is well defined, the author knows about it, and they're lying about their software's qualifications for it to deliberately mislead users and make themselves more money.
2. It’s not a fact, it’s a definition, as you’re stating it yourself. The thing with definitions and laws is that they can be changed if a majority agrees to do so.
Not sure if it’s the case here. You are probably right with the definition, but stop acting like you have the ultimate truth.