Some form of this disclaimer can be found at the front of nearly every novel out there as well as in the credits of most films and TV episodes. It's an attempt to stave off libel suits; it seems to have been originated as a response to a suit against the makers of the 1932 film Rasputin and the Empress by a Russian princess who believed one of the characters to have been modeled on her. Think of it as the more professional equivalent of I Do Not Own (though, as publishing companies and Hollywood studios, unlike fanfic authors, actually have lawyers working for them, it's more likely to carry some amount of legal force).