anyway lets resolve the internal issue first. You need to find out what your partners really want, chances are they want/need something else than what it looks like from outside, find out what will motivate them to stay with your project?, also it is not clear whether they prefer to quit or they prefer to change the concept, may be they want to quit because you're not flexible enough to listen to them and change the concept - you need to really listen to them and think rationally (not emotionally) whether changing the concept will benefit all, try to create a win-win situation for all. last option is to let them go (because if they are not motivated enough then it won't produce the desired result) without burning the relationship, find the replacement at the earliest. If they are united and want to close the company then find out the legal way to hold on to the intellectual property at the minimum cost to you....
if they are your true friends then they should not give you hard-time in exploring either options. If you really love your project then you have to be very firm though in a polite way so that they can figure it out that you're really serious to pursue your ambition and nothing can change your route (with or without their help) - may be they will change their mind after seeing your determination.