But a developer will only invest time if he knows that he will get payed.
That's the advantage of ordinary crowdfunding.
Your proposal is more risky... if he doesn't get any money, ok, the release
will be in a distant future, but so what?
He did the work unpayed...
it's hard to calculate that way or make a living of it.
But i guess your approach is very useful for not-so-professional development.
Like, if somebody wants to release the game for free (and as free software)
anyway, but with this try he may take the chance to get some bucks.
