His blog post describes how he implemented song matching in Java, with snippets of code. He said that while the code is not in a releasable state, he might clean it up and release it if there's enough interest.
About a week ago, he received a letter from Darren P. Briggs, VP and CTO of Landmark Digital Services, asking that the preliminary code be taken down and that no further code be posted.
Landmark Digital Services is a subsidiary of Broadcast Music (BMI), which acquired Shazam Entertainment's patent portfolio in 2005. It markets music recognition technology under the name BlueArrow.
"While it is not Landmark's intention to alienate those in the Open Source and Music Information Retrieval community, Landmark must request that you do not ship, deploy or post the code presented in your post," Briggs's letter states. "Landmark also requests that in the future you do not ship, deploy or post any portions or versions of this code in its current state or in any modified state."
In response to an e-mail sent to Briggs seeking clarification of Landmark's legal claim, BMI spokesperson Hanna Pantel denied that there has been any legal threat. "In response to your e-mail to Darren Briggs, Landmark had a private conversation with the Dutch developer in question, we have not pursued any legal action," she wrote.
Yet, the threat of legal action is clear. By refusing to take down his blog post, van Rijn risks an expensive patent lawsuit, or so Dutch patent attorney Arnoud Engelfriet told him.
EFF Fellow and patent attorney Michael Barclay agreed that posting code covered by a patent could put van Rijn at risk of a lawsuit, but noted that some critical details need to be determined.
"Merely posting the code on a Netherlands Web site would not infringe any US Patents," he said.
Landmark's claim, he said, appears to be overreaching unless the company has patents in the Netherlands. "If there are no issued Netherlands patents, he's free to ship and deploy all he wants in the Netherlands," he said. "The really sketchy part, and I don't know that this has ever been litigated, is he says don't post the code."