WordNet sense 1 (without concealment or deception; honest):

aboveboard

WordNet sense 2 (characterized by honesty and fairness):

square, straight

WordNet sense 3 (admitting of no doubt or misunderstanding; having only one meaning or interpretation and leading to only one conclusion):

unambiguous, unequivocal, univocal

WordNet sense 4 (extended senses; direct in means or manner or behavior or language or action):

direct