Ooh, interesting. As I understand it, Ronon is a civilian consultant. He's never taken oaths as a member of the US military, has no rank in the US military, and has no responsibility to follow any part of the US Code that applies to military but NOT to civilian consultants. So, DADT would NOT apply to him at all.

There's no citizenship requirement for enlisting in the US military (though you're not allowed to become an officer), but I have a hard time believing that the SGC would try to get the Pentagon to approve the recruitment of an alien. (And hi, even IF Ronon deigned to swear obedience to an entity he has no knowledge of, where are they going to send Ronon for basic training if the existence of the SGC is classified?)

So, yeah. Civilian consultant is the only way it makes sense to me.