If one looks at historic FCC regulation, it was always okay to listen to communications, but not to divulge the contents to 3rd parties. Even with just those older regulations, using data "heard" would be prohibited since that would involve transfer to others. I believe strong protections similar to wiretap laws were added for cell service, but unlicensed gear that has no protection from interference generally doesn't have any. For example in spite of an expectation of privacy, cordless phones are unprotected. Anyway, while there may be room to argue over access to certain communications being permissible, it's clear that one is prohibited from using anything heard (obviously including passwords, credit card info etc.)
The FCC rules for WiFi devices basically state that they must not cause any harmful interference and must accept any interference that occurs including that which may cause undesired operation. Read the manual that comes with any WiFi device and the text of that will be in there (the FCC rules require it to be).
The FCC rules for WiFi devices basically state that they must not cause any harmful interference and must accept any interference that occurs including that which may cause undesired operation. Read the manual that comes with any WiFi device and the text of that will be in there (the FCC rules require it to be).