To be fair, I think it's not that they aren't willing to change, the multiboot process actually does some setup/initializing prior to android's boot sequence that nitdroid depends on. uBoot doesn't do that setup, so the nitdroid kernel/bootup process would need to be adapted to work in that state. And probably I would guess working on that adaptation, when multiboot already works and is user-friendly, is not as important right now as working on things like making phone calls work...