As far as the "sexuality" of the characters is concerned, I've never caught the slightest hint that it was an issue. Sponge Bob's two best friends are a male starfish named Patrick who has weight and severe IQ deficit problems, and a female squirrel named Sandy who is a proud and loyal Texas girl. Between the two, the one that seems to come closest to a love or at least a "crush" interest is Sandy.
Personally, I'm getting really sick and tired of gays claiming innocuous entertainment as somehow exclusively their own. If they find the show funny (I think it's a scream) that's fine. But trying to insert their perversity, especially into childrens' entertainment, is infuriating. It's a not-so-subtle attempt to insinuate themselves with kids. Again, it's not the show itself, it's crap like this article that makes me angry.