Well, not sure if you know, but when you do a shot of tequila (in any situation) you're supposed to do the shot, lick some salt, and then bite into a slice of lime. It helps bring out the good taste of the tequila / makes it easier to stomach. So I'm pretty sure in this situation he's just meant to bite the lime from her. Can't tell from this gif what kind of mood the party is (college house party? bachelor party?), what the relationship between the two are (strangers? friends? dating?), or what any pre-arranged rules might be, so you'd really have to know those types of things to know whether or not it would have been okay for him to kiss her. The thing is, a lot of party games involve sexual stuff depending on the circumstance, but some are similar to this and basically harmless, like the game where you have to transfer a playing card from mouth to mouth by suction. I mean, obviously it's flirty and suggestive and there's alcohol involved, but that doesn't necessarily mean it's okay to kiss another player. Lips touching accidentally is probably fine. Idk why I just wrote all that when I haven't started my politics essay that's due in a few hours.