Linux kernel developer Christoph Hellwig has sued VMware in Hamburg, Germany, over alleged violations of the GNU General Public License.

Hellwig's suit, which is backed by New York-based advocacy group the Software Freedom Conservancy, alleges that VMware's proprietary ESXi hypervisor products use portions of the code that Hellwig wrote for the Linux kernel, in violation of the terms of version 2 of the GPL.

"In addition to other ways VMware has not complied with the requirements of the GPL," the Conservancy wrote in a blog post on Wednesday, "Conservancy and Hellwig specifically assert that VMware has combined copyrighted Linux code, licensed under GPLv2, with their own proprietary code called 'vmkernel' and distributed the entire combined work without providing nor offering complete, corresponding source code for that combined work under terms of the GPLv2."

This isn't the first time Hellwig has made such claims. He first accused VMware of violating the GPL in 2006 via the Linux Kernel Mailing List, even threatening to sue. It now seems that the proverbial other shoe has finally dropped.

Hellwig, best known as the maintainer of the Linux kernel's SCSI storage subsystem, is one of the top kernel developers. According to the Linux Foundation's latest survey, Hellwig has contributed 2,206 changes since version 2.6.11 of the kernel was released in 2005, making him the eighteenth most active contributor over the period.

The Software Freedom Conservancy is bankrolling Hellwig's lawsuit as part of its GPL Compliance Project for Linux Developers, although it says it views litigation as a last resort in such disputes.

"Sadly, VMware's legal counsel finally informed Conservancy in 2014 that VMware had no intention of ceasing their distribution of proprietary-licensed works derived from Hellwig's and other kernel developers' copyrights, despite the terms of GPLv2," the Conservancy wrote. "Conservancy therefore had no recourse but to support Hellwig's court action."

Hellwig is represented in his effort by attorney Till Jaeger of JBB Rechtsanwälte, a specialist in legal issues pertaining to open source software who has successfully litigated GPL violation claims in the past.

VMware, meanwhile, denies Hellwig's claims.

"We believe the lawsuit is without merit, and that we look forward to prevailing on all issues through the judicial process in Germany," a VMware spokesperson told The Register.

"VMware is an active participant and has a long-standing commitment to the Free and Open Source Software community. VMware dedicates considerable resources to ensure that its use of Open Source software is compliant with license agreements." ®