If the creator is not okay with you roleplaying their characters, cease immediately and find another character to roleplay. It’s really not that hard. You shouldn’t feel entitled to do what you wish with a character you didn’t even make, and you shouldn’t feel attacked for being told to stop. This also goes for real people. If the person you are roleplaying says they are not okay with it or openly state that they would not like people roleplaying them, then stop.