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Kevin Alderman didn't bring sex to "Second Life." He just made it better.

The 46-year-old entrepreneur recognized four years ago that people would pay to equip their online selves — which start out with the smooth anatomy of a Barbie or Ken doll — with realistic genitalia and even more to add some sexy moves.

Business at Eros LLC has been brisk. One of his creations, the SexGen Platinum, has gotten so popular that he's now had to hire lawyers to track down the flesh-and-blood person behind the online identity, or avatar, that he says illegally copied and sold it.

The $45 SexGen animates amorous avatars in erotic positions. It is software code, written in the scripting language of "Second Life" and placed in virtual furniture and other objects.

Avatars click on the object and choose from a menu of animated sex acts.

Alderman filed a civil lawsuit in U.S. District Court in Tampa, Fla., last month alleging an avatar named "Volkov Catteneo" broke the program's copy protection and sold unauthorized copies.

Alderman, who runs his business from home in a Tampa suburb, allows users to transfer his products, but prohibits copying.

"We confronted him about it and his basic response was, 'What are you going to do? Sue me?"' Alderman said. "I guess the mentality is that because you're an avatar ... that you are untouchable. The purpose of this suit is not only to protect our income and our product, but also to show, yes, you can be prosecuted and brought to justice."

Catherine Smith, director of marketing for "Second Life" creator Linden Lab, said she knew of no other real-world legal fight between two avatars.

However, Linden Lab itself has been sued more than once by subscribers over seizures of virtual property. In 2005, Japanese media reported that a Chinese exchange student was arrested for stealing virtual items from other players in an online game, "Lineage II."

"Second Life" isn't a game. There are no dragons to slay or other traditional game objectives. San Francisco-based Linden Lab describes it as "an online digital world imagined, created & owned by its residents."

Linden Lab provides a free basic avatar, a 3-D virtual representation of the user in male or female form.

Everything else costs real money. A 16-acre virtual island costs $1,675 plus monthly maintenance fees of $295. Virtual money, called Linden dollars, can be exchanged with real dollars at an average rate of about 270 Lindens per $1.

Avatars can be equipped with flowing gowns and tiny tattoos, and users with programming and Photoshop skills can reshape themselves into a virtual Greta Garbo or just about any shape imaginable. With a little cash, users can also have people like Alderman transform the avatars for them.

At Alderman's "Second Life" shop, shoppers can try out a dragon bed powered by one of his SexGen engines. Along with programmers and designers, he employs a sales staff who hang around the shop like real salespeople to pitch the perfect sex toys.

He is investing in a $25,000 motion-capture suit, a low-end version of one used to create digital characters in movies, to create more realistic sex moves for "Second Life" avatars.

As customers demand more real life in their "Second Life," though, these virtual creations can collide with reality.

"Virtually every aspect of real life is getting duplicated, and all the laws that can be applied to the real world are being applied in 'Second Life,"' said Jorge Contreras Jr., an intellectual-property attorney in Washington, D.C.

Last year, "Second Life" was rocked by a scandal over users who had modified their avatars to look like children and simulated pedophilia. Last month, Linden Lab shut down gambling in "Second Life" after concerns arose that virtual games of chance might violate U.S. gambling laws when members cashed in Lindens for real money.

Now comes Alderman's SexGen suit, which was filed July 3 and seeks unspecified damages. It accuses the unknown owner of the Catteneo avatar of violating copyright and trademark protections by copying, distributing and selling copies of Alderman's software.

Alderman's attorney, Francis X. Taney Jr. of Philadelphia, said the lawsuit has gotten a lot of attention because it involves sex, but is fundamentally about long-established law.

"It's a piece of software and software is copyrightable," Taney said. "It's also expressed in graphics, which also are copyrightable. There is some sizzle. People like to say it's really far out there, but at the end of the day I equate it to basic intellectual property principles."

Unlike many popular online worlds, such as "World of Warcraft," Linden Lab grants its users broad rights to create and sell content with few restrictions. Users can install copy protection and seek U.S. copyright and trademark protections, all of which Alderman did for the SexGen software.

"Whenever you create a situation where people are buying and selling things and potentially misappropriating them from their rightful owners, it is only a matter of time before the legal system gets called in," said Fred von Lohmann, a senior staff attorney at the Electronic Frontier Foundation in San Francisco. "This seems like a relatively straightforward case. It sounds like there is a real copyright issue."

Taney believes he knows who Catteneo is in real life, but is confirming it through subpoenas of records of eBay Inc.'s PayPal payment service as well as chat logs and trade history in "Second Life." He said Linden Lab and PayPal turned over their records, and he is preparing another round of subpoenas.

"We're proceeding carefully," Taney said. "This guy has claimed the information he gave to Linden was bogus. We are looking for ways to cross check and corroborate the information."

Catteneo, who did not respond to several interview requests sent through the "Second Life" messaging system, will likely have a hard time hiding.

"There is a whole lot less anonymity online than people think," von Lohmann said. "There are over 20,000 people who have been sued for downloading music. They may have felt anonymous, but they're weren't."

Alderman is unlikely to be the last to drag an avatar into court as the designers in "Second Life" try to protect their creations in the same way clothing designers such as Gucci try to eliminate realistic knockoffs

In recognition of the growing legal issues "Second Life" is likely to generate, the country of Portugal recently set up an arbitration center in the virtual world, though it has no power to enforce its decisions.

The legal issues may be similar offline and online, but von Lohmann said the trials could be a lot more interesting.

"In a virtual world, you have the ability to gather evidence you don't have in the real world," he said. "Everything that happens in 'Second Life' is reflected on computer servers. Depending on how long they keep the records, you could actually replay the event as it happens."