Prospero could've been hetero and just had a gay friend in Ariel. I'm hetero and happen to have quite a few gay friends.
Or perhaps (because Ariel is essentially Prospero's servant) the character of Ariel might be played as the prototype gay houseboy, a la *The Bird Cage*? :)
Anyone notice how the name of "Caliban" is *almost* an anagram of "cannibal"? If you misspell the word as "canibal", then it's a perfect anagram. And Caliban is quite a brutish character in the play, as well. As Prospero's other servant, Caliban is the antithesis of Ariel.
-- Nanaea