How can a program be in violation of DMCA? Is a knife in violation of the criminal justice system because some people use it to kill and therefore no one can use it anywhere, ever? How ridiculous.
They're probably claiming it's a circumvention device. Some knives (switchblades and gravity knives especially) are illegal in most places. I think the UK is even stricter.
I think it's usually about carrying them in public outside your house. Likely not as illegal to have them at home.
Gravity knives are scary in that the police have occasionally argued that certain common pocketknives (e.g. Leatherman) can be used as a gravity knife and arrest people (usually minorities of the wrong color). I once was going on a road trip across multiple states and had to research the laws of each state because I was carrying a Leatherman.