Guys, there's a big difference between stealing people's characters and recycling ideas.
When did the legend of Amleth become Hamlet before Shakespeare wrote it? When did Birnam Wood come to Dunsinane and Witches warn of men unborn before MacBeth was written? When did lasses from children's fables first get together to swap pornographic tales before Lost Girls? When did a League of Victorian characters unite against a common foe before LoEG? When did Marvelman first realize his entire past was a fabrication and he was the product of his worst enemy before Warrior comics? When did the Charleton characters get together in a Dystopian setting to face off against each other's ideologies before Watchmen? When did The Joker shoot Barbara Gordon through the spine before the Killing Joke? When did Mxyzptlk murder with malice before What Ever Happened To? When did Superman face off against a wonderful Satan analogue like C.W. Saturn before Miracle Monday?
These artists steal characters and settings to explore new ideas and themes previously unexamined in earlier renditions. That's the transformative nature of art. When it's obvious who or what the artist is evoking(outside of an homage) then it's derivative. The world doesn't need any more homages to Alan Moore, the guy's work is already influential enough.
So, its ethical for Moore to turn characters into versions the creators would not recognize nor approve of, its ok for him to expand on classic stories that had been told, its ok for him to tell a Joker's tale all because theft is the norm
but, for a comic book company to try and make money off characters they own, for modern day creators to want to tell stories based on other people's work, hell for DC to still be publishing books about the Joker, all of this is bad because DC is teh evil
no one was begging for a pornographic Alice book, just like no one was begging for Watchmen prequels, both are sophomoric exercises in childhood fantasies. The difference is DC is honest about it and Moore hides behind public domain and a manufactured mystique that pretends to make a team made of of late 19th century literature figures something more than what it was - a superhero book where he didn't have to actually create anything.