Not "basically" canon, confirmed canon. On screen, on the mouth, 'bout a good 10 seconds. Pretty sure there was tongue. Normally I wouldn't care either way, but that scene to even happen in an animated "children's" show on syndicated network television is a HUGE progressive step forward.
Legend of Korra and Steven Universe both had canonical LGBT characters, but in Korra they had to leave it at 'heavily implied.' While in SU they sing and cry and openly talk about their loves, but the one episode where 2 characters finally kiss the scene pans away last second. Granted that last scene played off the fact that Steven is young, and innocent, and awkward, and the scene itself was an allagory for watching your parents make goo goo eyes at each other, but who's to say if it was a creative decision or an excuse.
Link to the Adventure Time scene (Spoilers. Duh.) for anyone curious, btw