Seems to me that by telling you that he’s still with this girl and that it’s okay for you to date other people, that he’s trying to cover his own butt. Looks like he wants to keep both of you around, and this way he doesn’t feel guilty because you know about the other girl and he’s not pushing for exclusivity. I think a guy that was truly into you wouldn’t want you to be dating other guys, but that’s just me. I’ve had guys ask me to be the other girl, tell me they were on the ‘outs’ with their gf or that the relationship is rocky, that they’re on a break, etc. They’ll say whatever they think will get them what they want. If he’s seriously into you, then he’ll end things with this girl. Until then I wouldn’t get involved.