At first look, I like Thorsten's idea. If we could find some way to allow companies to spend just a little amount, in support of a specific library, and we could find enough companies willing to make such a contribution, then we could make it work.
I vividly remember many Amiga games where developed after a similar model. After presenting some demo and/or screenshot of the game in progress, the team would wait until they had confirmation that, say 500 people would buy the game.
I personally think, however, that that model was to insucure for the developers.
I remember seeing some online donation systems, where if the donation target was not met everyone got their money back. So there'd be no risk on either part. I can't seem to find the reference now though.