I don't really understand what the point of this is. The complaints largely seem to be "DC weren't respecting me, so now anyone can do what they want with this". One of the things he complains about is how they wanted to do something, thinking they owned the rights, he said no and then they couldn't do it. But... now they can, because it's now in the public domain.
Actually, all this is ignoring the fact that AFAIK, you can't just revoke copyright and put something into the public domain, you have to explicitly grant a non-exclusive licence to everyone instead. That's why all the CC style licences exist.
Except that now he's put this into the public domain, DC can also do what they want with it to the extent that anyone else can.
It doesn't hurt DC financially, other than potentially diluting the Fable brand because anyone else can also use it now. There's also a strong likelihood that DC do in fact own partial copyright over anything that isn't the comic - so any figurines, film spinoffs, etc., in fact anything that wasn't wholly created entirely by Willingham, even if he still owns the underlying IP, so people almost certainly aren't free to make copies of anything other than just the comics.
Also I don't understand why my comment (the GP to this comment) was been moderated down so much. Is it just that my opinion is unpopular with fans and so it was downvoted rather than debated? For instance, re my comment about public domain vs explicit license there are many articles like this: https://www.techdirt.com/2015/01/23/why-we-still-cant-really...
IANAL obviously, but nothing now stops me from selling T-shirts, figurines and lunchboxes of fable with my own drawings/designs. Any such sale is money not in DC pockets.
Sure, you can make whatever you want from the original designs (but note not from any elements from figurines or films or anything else DC made that deviate from the comics).
However, that in and of itself isn't depriving DC of anything, as they're no worse off financially than if whatever you make never existed. Arguably, if you create something that's a runaway financial success, and someone has to choose between buying your thing and the DC produced thing, then sure maybe then DC loses a sale. But sales are rarely binary like that. If you do something that promotes the brand, it probably benefits DC's sales as well.
The only thing that might actually impact on their profit is someone producing an exact copy of the original comics, at a lower price, and of better quality. Even then, people might still buy the DC version so it matches the rest of their collection. And if it is an exact, exact copy of the original comic, there's always a risk there might be something with a DC copyright on it, e.g. the font that's used in the title, maybe a reference to some other DC property, etc...
Actually, all this is ignoring the fact that AFAIK, you can't just revoke copyright and put something into the public domain, you have to explicitly grant a non-exclusive licence to everyone instead. That's why all the CC style licences exist.