A German court has granted a preliminary injunction against security firm Fortinet for allegedly violating the general public licence (GPL) and hiding Linux in its code.

The ruling could prevent the security appliance vendor from further distributing its products until it complies with the open source licence.

Fortinet was accused of using cryptographic techniques to conceal the presence of Linux code in its FortiGate and FortiWifi products, as well as not releasing its source code under the terms of the GPL.

The company's use of Linux was deemed by the court to be in violation of the GPL under which Linux is distributed.

The licence allows for the reuse of the code, but requires that developers grant public access to all the source code and provide a copy of the full licence text.

The case was filed in Germany against Fortinet UK Ltd, the UK subsidiary of Fortinet Inc, by Harald Welte, a Linux developer who also runs the gpl-violations.org website.

The site aims to raise public awareness about past and present GPL violations, and has resolved 30 such cases in the past months.

"This violation by Fortinet is especially egregious since the vendor not only violated the GPL, but actively tried to hide that violation," Welte claimed.

Fortinet said in a statement to vnunet.com that the company has been working to resolve the issue outside court.

"Fortinet is surprised that Mr Welte pursued a preliminary injunction against Fortinet in Germany and believes that this is an unnecessary action," said the statement.

But Welte insisted that obtaining the injunction was a necessary step in persuading Fortinet to take the issue seriously, and had ended negotiations about a settlement.

"Fortinet apparently did not want to believe that this is a serious issue," Welte wrote in his blog.

With the rise of open source software in the enterprise, companies increasingly run the risk of violating open source or commercial software licences by mixing internally developed code with software that is governed by the GPL or other open source licence.