Yesterday, the Munich district court granted a preliminary injunction against Fortinet's GPL in-compliant use of Free Software.
Fortinet is shipping a series of Firewall products (FortiGate and FortiWiFi) running on Linux without complying to the GPL.
Legal action was made possible via the "initrd" code, on which Werner Almesberger signed me his rights a couple of months ago.
To the best of my knowledge, Fortinet is not using any of the iptables/ip_conntrack/... code, but something different. We'll see how that is integrated into the kernel network stack as soon as they release the full corresponding source code in accordance with the GPL.
Obtaining (better: Applying) for a preliminary injunction is a tremendous amount of work, so this really is the last possible option if all other options have failed.
Also, making this issue public with a press release was a very well-thought action. Fortinet did not even sign a declaration to cease and desist within four weeks after receiving the warning notice. They apparently didn't want to believe that this is a serious issue. Maybe the public pressure will help getting them back to negotiations.