I personally wouldn't let my boyfriend dance with girls I don't know, but if they're my friends and I trust them I wouldn't care, as long as they're not grinding on each other. 

He doesn't even want to dance with me why would he want to dance with other girls? Lol he's embarrassed because he doesn't know how to dance! I force him into it at wedding and stuff because I love dancing!

Never 

Nope, nope, nope. I would never be ok with that lol.

Of course that's fine! Its horrible to be at a party and not dance with anyone. I'm all for it. It does depend on dancing if she's all over him its not okay but seriously let him dance with them. Your friends will love you even more for it. Don't stare at them when they dance. It's lonely if there isn't anyone to dance with and if most of the songs are slow especially its nice to get to dance once with someone.