So assuming OP=ConnectU, the legal issues the OP's afraid of is that his partner will fork the existing code into something successful, even though OP has done most of the work thus far.
At least this is how I interpret it. Please correct me if I'm wrong!
If his partner can fork it and build something successful faster than OP, then the OP isn't the productive one and his current deadbeat partner is, the premise of OP is invalid.
Based on the original post, the OP thinks he is the one that can deliver and that his partner can't. If OP can't deliver a product that people want, none of this matters.
That's all I'm saying. You're assuming that ConnectU would have been successful if Facebook hadn't happened. I don't believe that to be the case.
I thought of this analogy in terms of existing code (rather than being able to deliver, because OP's partner could take the idea and find someone else to do the code). The OP wrote the existing code, which is allegedly what happened to ConnectU. Of course, if you discount the allegations and assume that Zuckerberg wrote the code himself, then the existing code argument is irrelevant.
This is an interesting debate that can actually be answered if the OP chimed in to explain what he meant!
Re ConnectU: I never assumed that ConnectU would have been successful if Facebook hadn't happened. In fact, I believe that the only way ConnectU would have been successful is if Mark Zuckerberg stayed on that project (or _maybe_ if ConnectU made him sign a NCA).
Then he'd be the one in the team that wasn't delivering. We're taking OP at face value and assuming he is the one that can deliver a product that the world likes and that the other person is lacking in that area.