The world configs are just json files with a list of the biomes and what not for the planet. The world builder lets you create these using a node editor, but the output is still just a json config file. which is why i was asking if anyone had looked into making one.
Some one with some good JqueryFu should be able to look at those and then figure out some sort of web based creator that spits out a config file.
Heureka has been making custom planets on his local universe Some shots from my worldbuilder tests - #191 by Heureka so all the pieces are there, im just way to lazy to bother trying to figure something out.