It sounds like you don't have a written contract. I think you are legally in the clear, but if you become wildly successful, the guy might give you grief about it at a later date.

(A la "I once sat on the bus next to your sister's best friend from high school -- please buy me a house!" that star football players find themselves subjected to. If the company becomes a household name worth scads of money, everyone that ever discussed the idea with you may try to claim part ownership.)

So I would try to handle it diplomatically and also get something in writing in some fashion making it clear that his involvement is ending, if only by email. Maybe send a friendly "Hey, buddy, thanks for (whatever small role he has actually played), but the project is at a point where I need a more involved partner. Given your track record so far, you clearly don't have the time to be that involved. So this is just to let you know that I am moving on and you don't need to worry about this project anymore. I will be seeking someone with more daytime availability and sales skills as I have identified those as areas of need for the project.

Make it clear you are ending his relationship to this project. Make it clear he really hasn't done much. But also try to frame the email like "Just letting you off the hook so you don't have to worry about this anymore."

You say he is outgoing. Some people genuinely feel some sense of social obligation because someone asked them that one time and they don't know how to say 'No" and they feel like you will be crushed if they "reject" you. Sometimes letting them know that you are fine without them let's them breathe a sigh of relief and move on.

But don't do it verbally and keep a record of the communication. That will help create a paper trail should this ever end up involving lawyers for some damn reason or other.