he is in many ways quite emotionally immature for his age.
He has a healthy interest in girls, although he doesn't have much of an idea how to go from fantasy to reality yet.
Industrialization moved that age back, but our bodies don't know that.
I've recently noticed myself thinking of college graduates as emotionally immature.
There’s Webkinz, a world based around the virtual alter egos of the plush toys found in stores.
There’s Poptropica, a fantasy archipelago where kids ages six to 15 roleplay and complete quests.
I'd also advise you not to get hung up on whatever they want to call their time together.
I think it takes a conscious effort to realize that teens have adult feelings even if they don't yet have an adult sense of responsibility and self-control.
When her 10-year-old daughter announced that she had gone on a date to the park with a boy and he’d asked her to the prom, Rebecca Levey was astounded.
From what you've described, it doesn't sound much different --at this point --than when kindergarteners decide they are "boyfriend and girlfriend." It does sound, however, like this might be a good time to have "the talk" (about sex) if you haven't already, since he's moving quickly towards physical maturity.
(This piece of advice is completely independent of his relationship with this particular girl.) As far as "when can he date," I'd tell him when he can drive himself and his date to the movie, pay for dinner himself, and generally show evidence of being able to handle himself in a responsible manner without a parent.