Under "Fair use" you can quote song lyrics, refer to songs and other aspects of popular culture for a variety of ambigious reasons and even more ambigious when "art" becomes involved. Given that copyright laws in general are insane, it's personal and non-profit use, chat is temporary appearance of it and you'd be allowed to do it at a gaming table I am going to include (until told otherwise) roleplaying in that.
You can quote or sing lyrics if it's appropriate to your character in the chat just as you can have your character drink a Pepsi or own a Playstation, etc. As a cultural reference it's fine, the only thing that it may become a concern in is if you include large amounts of a song, short story, etc into a forum post then if there is seen to be a problem we will require them to remove it.
Also please note that since the site itself would not count as personal we will not be including any brand names in the menu, room descriptions. This is an issue where the site itself may have to worry, but generally users will not provided there is no abuse and the material itself doesn't violate the rules of the CoC etc.
