One obvious way is taxation. It's the same way we fund expensive photographs of space, and high-quality journalism, and world-class educational materials... all of which contribute to the common good, like these insect photos.

There are many other ways. Is it hard to think them up yourself? Private foundations, crowdfunding, tangential services and showcases (he's already doing that), etc...

This isn't some novel idea, it's how a great amount of our works are produced today even though we also have copyright. Without copyright, we would lubricate different models for the knowledge economy. It's not like the world could only possibly be the exact way we do things now.