Note: Before reading this page, familiarize yourself with the KGS Terms of Service.
KGS do censor their users, and they might and frequently do boot people off for anything that the admins deem offensive.
Using traditional foul words like gets one banned quickly, and people also banned for using abusive language.
KGS restricts you from abuse of others and the use of obscenities only in public rooms, where there are often many children present. You can do anything you wish in a private room. The policy is implemented to create a pleasant environment in which to play while, at the same time, providing a venue for people to behave as they wish in private. The admins are very tolerant of most chat but will come down hard on people who deliberately create an atmosphere which is unpleasant for a significant minority of its members. The terms of service are clearly set out and offer very few restrictions: abuse and obscenities are the two significant ones. By playing on KGS you implicitly accept the TOS.