Finally, they've put up more details on the next update. I'm stoked :D
Technically they're not the first MMORPG to offer player created content - that would've been Ryzom Saga (with its Ryzom Ring). Nor are they the first MMO to offer it, either. Second Life wouldn't be anything without its community making and creating things.
First major MMO? Okay, I can give them that.
Anyhow, they've got a page linking to all the official information, plus a video from Rooster Teeth. And check the Dev Journal for more information...