Warning: I am not a business type, so take the following with a grain of salt:
It is possible to form a non-profit corporation, which could hold the money that anyone was willing to contribute in a fund. If the deal never happens, we liquidate and everyone gets their money back (less whatever fees are incurred). If we do get the license, well, we have the license

Obviously this doesn't address the issue with
raising this kind of money. And overseas investors may cause a special problem, I don't know.
A couple people have pointed out the "free blender" campaign. That was done in the Netherlands, IIRC, so laws are probably different than in the US.
Just some things to consider.
Coincidently, my company (the one I work for -- I don't own it) just got bought for $435M in cash, which means my options should finally be worth something. Not much -- it'll probably be an extra couple months pay -- but this might be the right time for me to invest in something worthwhile

I can't commit to any kind of number yet, 'cause I haven't seen one.