Basically yes, but not only swearing, it could also be if they're talking about specific people in the 'outside world', or mentioning particular brand names, or singing songs I think. That's why the "live" streaming is actually delayed (by 15-20 minutes, I think), so to give them time to work out what needs to be covered up.
i also found the live streaming going down or silent if the housemates are arguing or messing about which is kept until the highlights - ive seen huge chunks of arguments being edited out of the programme and as the audio is off you cant tell if the characters are portrayed in a certain way - or am i just being paranoid!!