A brief overview of the documents can be found at Dragon Avenue.
UPDATE: Phil Reed, of Ronin Arts and SJ Games has made his opinion clear:
After reading the license five times my reaction is: Hell, no.
I cannot see myself ever using this license. This license is very, very bad for anyone except WotC.
UPDATE 2: Wolfgang Baur is also not impressed:
And at first glance, the GSL is absolutely terrible for Kobold Quarterly. I'm not sure it will matter much for Open Design, as the Wrath of the River King will be in a separate product line.
I was hoping for better. Bah.
UPDATE 3 (expect a lot of these, and thanks to the Chatty DM for the link): Eric Mona (scroll down) of Paizo doesn't seem too thrilled either:
WotC is basically saying that they can yank the rug out from under you any time they want with this license. Is that how it reads to everyone else?
Yes, that's my take.
I don't think I would publish under this license if I was in this industry, professionally speaking.
That's my take, too.
UPDATE 4: Chatty is all over this like white on rice. In the comments of his post, he's linked to where Clark Peterson of Necromancer Games has been discussing this issue over at ENWorld:
It seems far less clear than I hoped, thats for sure. It also doesnt have that "safe harbor" feel. It has that "there are lots of ways for you to screw up and then we terminate you" feel.
My initial reaction: Not as clear or friendly as I wanted. In fact, it feels like "we want you to support 4E but we dont really want you doing anything interesting or being too successful." Which smacks more of corporate fear than it does of vision.
This is also interesting:
Clearly, as I understand that existing license, there wont be a "Tome of Horrors" for 4E. I'm not losing the right to make an OGL version. Period. In fact, I am pretty sure that I will be announcing a full color Pathfinder version of the Tome of Horrors shortly. That said, I am still considering a monster book for 4E.
Sounds to me like they had some good headway made on a product, and then this license may torpedo it. So they'll just repurpose the assets and release under another license, once certainly to be more amicable to their needs.
UPDATE 5: James Mishler of Adventure Games Publishing also isn't getting any warm fuzzies from the GSL:
Well, after reviewing the 4E GSL, I can say pretty unequivocably that Adventure Games Publishing will *not* publish any 4E Dungeons & Dragons products. At least, not under the existing GSL, nor under any GSL that even remotely resembles the existing contract. By the terms of that contract, you essentially turn your company into a Wizards of the Coast subsidiary. Not gonna happen with AGP.
AN UPDATE OF UPDATES: The RPG Blog II has a bit list of the latest reactions to the GLS announcement, including a further update from Necromancer Games and Chris Pramas detailing a product Green Ronin won't be making.