If you're a P2P developer looking to understand the law, the best paper on the subject has been my cow-orker Fred von Lohmann's "IAAL*: What Peer-to-Peer Developers Need to Know about Copyright Law." It's been out of date for a couple months, though, ever since Fred won the Grokster case, legalizing an entire class of P2P networks at a stroke. Now, Fred has revised the paper to reflect these new freedoms — have at it!
n other words, a copyright owner has to show that you had knowledge of infringement when you could have done something about it. StreamCast and Grokster (like vendors of photocopiers and VCRs) never had knowledge of a specific infringement at a time when they could have prevented it. The critical factor was the decentralized architecture of the Grokster and Morpheus software. The software gave the defendants no ability block access to the network, or to control what end-users searched for, shared, or downloaded. Accordingly, by the time the defendants were notified of infringing activity, they were unable to do anything about it (just as Xerox is not able to stop infringing activities after a photocopier has been sold). In the words of the court: "even if the Software Distributors closed their doors and deactivated all computers within their control, users of their products could continue sharing files with little or no interruption."
