Is there any way you could offer to _buy_ the code from your cofounder ? If he/she believes there is no value in it (hence the pivoting), there shouldn't be any problem.
I had thought of this. Unfortunately I think his price will be exorbitantly high based on the time he put in. I also am not convinced that there is really much value in the code itself, it just puts me slightly ahead of square one in a new venture. Based on some comments it sounds like the code without the developer is actually quite worthless, so I'm coming around to it being OK that I don't have any rights to it should I leave.