Code Microsoft released this week for the Linux kernel under the General Public License version 2 (GPLv2) was in violation of that licence before Microsoft made it available, according to an open-source network engineer.

Stephen Hemminger, principal engineer with open-source network vendor Vyatta, claims in a blog post that a network driver in Microsoft's Hyper-V virtualisation software used open-source components licensed under the GPL.

Since the license does not allow for mixing of closed-source or proprietary code with open-source code, the software was in violation of the GPL, he said in the post, which details how the violation was discovered.

"This saga started when one of the users on the Vyatta forum inquired about supporting [the] Hyper-V network driver in the Vyatta kernel," Hemminger wrote. "A little googling found the necessary drivers, but on closer examination there was a problem. The driver had both open-source components which were under GPL, and statically linked to several binary parts.

The GPL does not permit mixing of closed and open source parts, so this was an obvious violation of the license."

Hemminger said rather than "creating noise," he alerted Novell to the violation, which then informed Microsoft of the matter. He also congratulated Microsoft for releasing the code, which consists of four drivers that are part of a technology called Linux Device Driver for Virtualisation.

"It took longer than expected, but finally Microsoft decided to do the right thing and release the drivers," he wrote.

Microsoft said that it is working on a response to Hemminger's claims. Novell did not immediately respond to a request for comment.