2) 'If I don't charge for it, it's not a violation.'
False. Whether you charge can affect the damages awarded in court, but that's essentially the only difference. It's still a violation if you give it away -- and there can still be heavy damages if you hurt the commercial value of the property.
3) 'If it's posted to Usenet it's in the public domain.'
False. Nothing is in the public domain anymore unless the owner explicitly puts it in the public domain*. Explicitly, as in you have a note from the author /owner saying, 'I grant this to the public domain.' Those exact words or words very much like them.