Simply say you have your own ideas that you're working on... which I'm guessing is more or less true, and you simply have no spare time. You might point them t

Simply say you have your own ideas that you're working on... which I'm guessing is more or less true, and you simply have no spare time. You might point them towards an commercial app dev shop, probably a big favor to them as they'd have to do their own leg work and learn a bit about the economics involved.