I don't think that ID is an open movement, even if there is little visible formal organisation. I know of at least one ID supporter who said that he had been invited to leave the movement because his views were considered unacceptable (although Behe hasn't been asked to leave despite straying a long way from orthodoxy).
And whether there is a formal movement or not the term ID is so strongly associated with the Discovery Institute crowd that I think it would be foolish for anyone who did not follow the party line to claim to support ID.