Whether or not you should be mad .. is based on what the "rules" were. Did you state that you would always have to be together when anything happened? If not.. then you probably do not have the right to be mad. Would you have made out with a friend if he wasnt there? Plus.. you getting upset could mean that you arent ready for an open relationship. A lot of people can make an open relationship work.. but most cant. I know just from threesome experiences that .. it can be a really bad situation...if its not something you are really ready for.