Google has threatened legal action against YouTube-MP3.org, a website that converts the audio tracks of YouTube videos into downloadable MP3 files.

The website's founder, Philip Matesanz, posted an appeal for assistance and insists that recording streamed files for personal use is legal in Germany, where his website is based.

Google characterizes the issue as a simple terms of service (TOS) violation, something the company deals with on a regular basis. "We have always taken violations of our terms of service seriously, and will continue to enforce our terms of service against sites that violate them," a YouTube spokesperson said via email.

On that basis, the case seems to be fairly clear cut. YouTube's TOS state: "You shall not download any Content unless you see a 'download' or similar link displayed by YouTube on the Service for that Content. You shall not copy, reproduce, distribute, transmit, broadcast, display, sell, license, or otherwise exploit any Content for any other purposes without the prior written consent of YouTube or the respective licensors of the Content. YouTube and its licensors reserve all rights not expressly granted in and to the Service and the Content."

[ Read Google Sees Surge In Censorship Demands. ]

However, Matesanz maintains that his site does not use the YouTube API, so he is not bound by the API TOS, and he insists that YouTube's general TOS (excerpted above) doesn't apply either.

"This TOS has nothing to say about audio extraction but forbids [making] YouTube videos available for download, and that's something I don't do since I just provide the audio stream," he wrote in an email.

While users of Matesanz's website appear to violate YouTube's TOS by downloading YouTube content in the absence of a download button, YouTube-MP3.org might conceivably claim not to be involved in downloading. But it's hard to see how YouTube's lawyers couldn't make the case that YouTube-MP3.org is copying and reproducing YouTube content in contravention of the TOS.

However, Matesanz insists that YouTube's general TOS does not apply to those who don't have YouTube accounts. "In Germany, it's the case that you are not bound to a contract (TOS) as long as you haven't accepted it," he said. "YouTube is a public broadcasting site, you don't need to accept [its] TOS to use [its] service and therefore I am not bound to it, like every user that is not registered and hasn't agreed [to] the TOS."

Moreover, Matesanz claims that German law permits personal copying of broadcast content. "There was [an] online service that ripped the TV stream from satellite and the users could download it then," he explains. "The respective TV station sued the service provider but our highest court has ruled that his service is not any different than a hardware-box you connect to your TV and rip the signal with it instead. It's the same situation for my service as well."

An article published in Die Welt last year supports Matesanz's argument. It says that German law allows both the recording of digital radio broadcasts and the downloading of YouTube videos.

Kurt Opsahl, senior staff attorney with the Electronic Frontier Foundation, said in a phone interview that he couldn't immediately evaluate Matesanz's claims about German law. In the United States, he said, most cases on the applicability of TOS agreements focus on whether there was an affirmative act, like a click on a button, to signify assent. He says there are also what's known as browse-wrap contracts, that assert the user agrees to the terms by using the site, but adds this is harder to prove.