They are people at various stages of making the transition from man to woman. I believe that "inter" comes first, then "demi" and finally "trans."
Anyway, they are key to my plan for the festival. Regrettably many of the events are "women only," but the website clearly and specifically states that inter- demi- and trans-people are welcome. So as far as I can see, that means that a man who is in the middle of becoming a woman can attend, right?
Now, becoming a woman is a long and arduous process, and "inter" people are on the first stages of their journey. So what if a man had only just started becoming a Lesbian, for example taking just one hormone pill or having just one counselling session? Surely that would qualify them as at least an "inter," and thus entitle them to attend all events, including even Club Diva! As long as they are becoming a Lesbian rather than a straight woman obviously, but I foresee no problems there.