No, it isn't broadcasting an "invitation". That is YOUR misinterpretation. It is broadcasting an identifier. You are free to intercept and read the value of that identifier. That doesn't give you license to pursue a connection to the equipment that did the broadcasting.
If you happen to intercept information while sniffing the packet streams, you are constrained by the Communications Act of 1934 not to divulge anything you might learn without the explicit permission of the parties communicating. You can and will be prosecuted if you use that information. Ignorance of the law is no excuse.
LOL! Connecting to an open wi-fi is not "sniffing the packet streams." I'm not sure that you even know what you are talking about at this point.
It IS an invitation. Why are you broadcasting it other than to invite connections? You already know it and any computer you want to connect to it already knows it. It's only purpose is to solicit new connections. That's why you are supposed to turn off broadcasting it if you don't want anyone else to use it. Duh.