I think it's better to get it done.
Firstly, and maybe most importantly, because it's a source of badness in your friendship. The longer it goes on, the more chance you feel resentful of your friend for not following through, and the more chance they feel bad about saying they'd like to do it, and not being able to, and that starts to breed resentment on their part too.
If somehow something happens in the future, and your friend gets some spare time/motivation/whatever to contribute again, then they can always ask if you'd like to try again.
Aside from that though, if you've cleaned up this situation, then your slate is clear: you're not putting energy into this problem, and you're free, both time-wise and mentally, to seek out a new partner. That's the best thing for your project.