Short version: Bill Willingham created a popular and successful comic book series called "Fables" 20 years ago. It was published by DC Comics but, unlike writers and artists who work on Superman and Batman, Willingham owned the intellectual property and copyright to his work. There's no dispute about that.
After years of being (as he describes it in the linked piece) frustrated, lied to, and cheated by his publisher, today he dropped a nuke and made "Fables" public domain. That means anyone in the world has the right to use "Fables" characters and tell "Fables" stories however they want--prose, comics, cartoons, movies, puppet shows--anyone but Willingham himself, ironically, who's still bound by his contract to only publish "Fables" with DC. "Fables" now belongs to the other 8-billion-minus-1 people on the planet.
Wow. Geez. I've never heard of a creator doing that,* but can't think of a reason it's not legal, ethical, and the biggest middle finger Willingham could possibly flip.
To me, it highlights the power creative people have and are often willing, even eager, to give up. My literary lawyer explained it to me like this: when you create something, you hold ALL the rights to it. If someone such as a publisher wants it, they will negotiate to pay you for YOUR rights. More rights should cost more money. YOU hold all the cards, even though it sure doesn't feel like it when you're desperate for your first book deal and it's the only offer on the table. It's hard to believe, but they really do need you more than you need them--as long as you're willing to walk away with nothing. It's even harder to believe, but no deal is better than a bad one, as I've learned from friends who've made bad deals.
A publisher isn't your boss. They're your business partner.
(*Tom Lehrer, whose smart, satirical songs were very popular in the 1950s and '60s, recently made his entire catalog public domain, but not because of a dispute with anyone. He's apparently just a really cool guy.)