The legal foundation of P2P is "substantial non-infringing use" - here's a pretty substantial use and the only people being "infringed upon" are Iraqi troops:

Various forms of peer-to-peer technology, which allows computer users to bypass central servers and connect directly with one another, are being used to plan battlefield operations in Iraq and deliver humanitarian aid.

Microsoft Corp.'s NetMeeting software and programs from Groove Networks Inc. and Appian Corp. are part of the military's shift away from massive central computer servers toward more flexible models that let users work on joint projects and share information — even when they are cut off from high-speed communication links.

Commanders in the Persian Gulf use collaboration software to chart progress, drawing on one another's maps during videoconferences several times a day, said J.P. Angelone, who heads the enterprise capabilities center at the Defense Information Systems Agency.

The data are kept on individuals' computers instead of a central server. When one person disconnects from the network, he can keep working on a personal version of the material. Logging in again automatically sends updates to the other participants.

"It's helpful because you reduce the physical distance to connect," Angelone said. "If you've got a command or a tactical unit in the area of responsibility, there's no sense coming all the way back to tap into a server."

The technology is largely off the shelf, relying on NetMeeting and audio and video add-ins for computers.

"Peer-to-peer" is a catchall phrase that describes a general approach; the actual systems vary widely in the way they're set up and in how decentralized they are.

The defunct song-swapping service Napster, for example, was a hybrid system that used central servers to direct its users to one another and then dropped out of the picture. A successor service, Gnutella, is more purely peer-to-peer, with no central index. Individuals use the Internet to find one another through small hubs, without a single point of failure that could crash the entire system if it shutdown.

....Coordinating the efforts toward decentralized computing is the Defense Information Systems Agency, which has installed basic collaboration tools at more than 63 sites worldwide. The Defense Collaboration Tool Suite already includes half a dozen commercial programs, and companies backing 17 more have asked to be considered, said the agency's Angelone.

"We want to help everyone inter-operate and be able to share information across the networks so they can collaborate with other commands with the tools of their choice," he said.

Angelone and others said peer-to-peer's progress toward the battlefield would continue because such systems are more resistant to attack and can be faster and easier to use than traditional, server-based setups. [LA Times]