Virtual worlds are endlessly mutable. As are the wildly implausible schemes their boosters concoct for making money off them. The latest idea Linden Lab has for Second Life: Profit, in some vague, unspecified way, from the world's free 3D design tools. The perpetually gullible BusinessWeek bought this story, pointing to examples of toy designers and architects building digital models and showing them off to customers in Second Life. There's a certain beauty to it: An entrepreneur's fantasy, used to peddle other entrepreneurs' fantasies. Not that there's much of a business here, since Linden Lab gives away its design software.It does suggest a graceful exit strategy for Linden Lab's investors, which include Benchmark Capital: They should persuade Autodesk to buy the company before its free design tools erode the market for that company's profitable design software. Not that I think that Second Life actually poses a threat to the AutoCad franchise — just that Mark Kingdon, Linden's adman-turned-CEO, is slick enough to make the pitch.