The developers work for free.It would be a good idea if people could donate directly from their wallet through some agreed tax or interest on holdings.Why should anyone work for free?
Crowdfunding the hard fork is a good idea, but keep in mind that the monetary reward for developers would be given as an equal amount of their NMC balance in OSIRIS. However you did bring an interesting point regarding the wallet, because since both NMC and BTC use SHA-256, it would be technically possible for the OSIRIS wallet to have an order book that atomic swaps between BTC and NMC.