I think invisiblehand has it right. The Curl is not a copy. It has a similar fold. It is like when Schwinn had the so called cantilever frame. They patented and no one else could have it. When their patent ended everyone copied it. Outside of the painted names and badges the bikes were the same.
All of this is for the good of the consumer and enhances innovation. Without the patent, inventors would be discourages. Without the patent ending, innovation would be discouraged. Hopefully this presses Brompton to step up their game.