Formally, it's the Code of Conduct, but that just contains the normal stuff. Y'know, be nice, be polite. It definitely doesn't contain specifically things that are on/off topic and is probably not what you're looking for.
Closest I could find is probably from the reply of one of the moderator:
Plus fewer people are interested in Apple's framework here anyway. It's more like you wouldn't get much help or attention here, than it being forbidden.