A federal court today ruled in favor of people using file-sharing applications such as Napster and Kazaa, notorious for illegal distribution of music files.

The ruling was a blow to the Recording Industry Association of America, which has been combating users and developers of this software because of its potential to illegally distribute copyrighted material.

In essence, the ruling states that merely making music files available for sharing does not constitute copyright infringement. The case, Atlantic v. Howell, centers on Jeffrey and Pamela Howell, a husband and wife that had Kazaa installed on their system. Mr. Howell asserted that the software itself had sought music files stored on his system and put them into Kazaa’s shared files folder.

Indeed, it was unclear to the court which Howell (if any) had designated the files for sharing. On those grounds the court rejected the RIAA’s position that having such software on a system constitutes infringement. Similar rulings have come down this year in Massachusetts and Connecticut, and last September in California.

But in Electra v. Barker, a New York court on March 31 ruled that having such files “might” constitute infringement, even if no one has copied the files. The court stated that “an offer to distribute” could be enough to constitute distribution and violation of the copyright holder’s rights. I suppose it could be thought of as akin to “possession with intent to distribute.” Apparently the courts are grappling with differences between the terms “distribution” and “publication.” The issue remains an open question.