I get the feeling you don't want to drop this, which I appreciate. The thing that strikes me is that it sounds like the other guys involved in the project were

I get the feeling you don't want to drop this, which I appreciate. The thing that strikes me is that it sounds like the other guys involved in the project weren't involved. Think of them as your long-term business partners. You're supposed to be starting a start-up with a team, not with a bunch of coaches, an owner and one player. At the same time, having been an SE, a PM, and a CEO, I do know that sometimes different roles don't understand what everyone is doing. It sounds like you have a very good handle on SE & PM roles, and I suspect you are correct in your thinking when you say that the other guys haven't been pulling there weight. I think this is what you want to dig into. I'd have a chat to the investor about how he see's the company and team progressing, without complaining about the partners. Perhaps he can give some insight into why he believes in the team, maybe something you are missing. Be cautious of how you bring up "concerns" with the investor, as you don't want to damage the relationship. A few good things could happen. Maybe you get a better feeling for how the investor sees things panning out, and are convinced that whatever you are working on has legs. If not, perhaps the investor has other investments where you may be a good fit as an engineer. Perhaps you take the demo yourself and talk to some would be users and get feedback (I'd do this anyway). Doesn't mean you're stealing the code and going rogue, but you want to know what a potential user thinks of what you made. From there, you can also decide if this is a good thing to continue working on (I agree with all the comments that have said you should be able to sell without a demo). Best of luck