+1 for this... Xamarin seems to make most of their money going the other way with monotouch, this is a proven way to revenue.
I guess ideally this would need a company that is the equivilent of Xamarin to drive this and objective C forward onto the other platforms.
I don't really see why; GNUStep is already an established FSF project, and I see no need for a company. What it needs is a bit of attention, which is what this kickstarter will hopefully achieve.
A modernised GNUStep could allow easy ports of a lot of MacOS software, both open and closed-source. That in itself might be enough to kickstart a non-MacOS ObjC/Cocoa ecosystem.