From Brickset:
LEGO partners with Tongal to launch LEGO World Builder
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So apparenty it's a site to pitch entire themes to Lego. Simillar to Ideas, but projects don't automatically get reviewed once they get a certanin number of supporters, so there isn't a public review phase and all that. Other users can also contribute to a project. Also, 3rd party licenses are not allowed.
What do you think?