Katzer initially threatened Jacobson and JMRI with a patent infringement lawsuit in 2005, and demanded hundreds of thousands of dollars in licensing fees. Upon investigating Katzer's claims, Jacobson was surprised to discover that Katzer had misappropriated significant amounts of JMRI code, using it without attribution in a commercial software package. Jacobson retaliated against Katzer's patent suit by filing a copyright infringement suit.
The case has attracted considerable attention within the open source software community because it has broad ramifications for open source license legality. A federal appeals court that heard the case in 2008 ruled that violating the terms of an open source software license constitutes copyright infringement, not just breach of contract. The distinction is important because the legal remedies for copyright infringement are generally stronger.
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