[eksith]

Are you sure he's trying to muscle in at the last minute or maybe he's just shooting the breeze after months of silence?

Run. That's what you want anyway.

Say and that you've moved on to bigger and better things, which you are, and that even B has moved on as well. It was fun while it lasted, but ABC is no more.

I'm not entirely sure if lawering up will mend relationships, but it's the least painful way to complete a breakup. The idea was originally thought up by B, and B has given your authority to move on. That by default makes it simpler and since you were never formally a "company", this makes it almost a non-issue. But if he causes too much noise, that's your alternative.