Oooh, I see. Yes, it does kind of read the other way (or either way, I guess!). Have you been in contact with him since this? And I suppose the same question applies from before, simply gender-changed - do you like him in terms of dating, or were they just passionate, drunken encounters? If she's your best friend then you have to decide what you really want, as unless she's incredibly giving and accepting I can't see her supporting you with that.
Again, although they've been dating for years you said they were very on and off, and you're all young (I presume); I'm not pretending the situation is ideal but 'first' or not they don't seem completely solid and whilst that's no excuse things could have been worse, especially as you didn't actually have sex. Yes, there's still trust issues and I'm not pretending that's not a big deal either but you stopped yourself and that's something. Since they were drunken encounters (and since you didn't actually have sex) they may very well get back together; it's too early to tell right now, presumably? In either instance I suspect she needs a little space to think things through.
If they hook back up you need to respect that and perhaps distance yourself when they present themselves as a couple. I don't know if they tended to do their own thing much of the time or were almost always together, but it would be too awkward any other way. If they don't hook back up then it's still not really a good idea to see him again (if you don't actually want a relationship), and it goes without saying you need to monitor how much alcohol you drink; it affects everybody in different ways but they usually all end in trouble!
Try not to feel too bad - you're young and enjoying life. You said she's forgiven you (twice!) which must show a strong friendship, and there's no guarantee they won't get back together again in X amount of time, if they're meant to be. Chalk it up to a life experience and try and move past it. Life is all about learning as well as living.
There's that smell again...