It looks like Sitecom GmbH got themselves into trouble by not understanding what are the obligations of using GPL-licensed software.
Once again we are reminded that freedom does not equal anarchy. GPL-licenced software is not public domain software; it is free for the taking, but when you start modifying it, you are asked to share your modifications with the world.
Fortunately, there are more business friendly licenses, like the BSD license and its many variations. They are particularly suitable for embedded systems, hardware firewalls, etc.
Sitecom probably wouldn’t have gotten themselves into this legal knot if they used pf.