I still don't understand how Brompton manages to use copyright to protect their fold (the patent is long gone) since one of the principles of copyright is that form-following-function is exempt. You can't make something that folds in the same way without it looking enough like a Brompton for them to call their lawyers. Unless you're in China, of course, where copyright is an irrelevance.
Brompton has learned the hard way that the Dahon Curl offers enough of a difference to be legally sold in Europe whereas Chedtech has learned the hard way that their Carbon Brompton clone is too close to the original. Something that other cloners had to learn
years earlier as well (the patent had gone back then already). At bikeforums.net recently there was an interesting thread about
"Andrew Richie styled folders" (well it was interesting in the beginning until it went berzerk). There was an extensive but still not comprehensive list of "brands" that build clone Bromptons in it. The interesting thing is that in my eyes all those cloners really try to build purposefully a "fake original" whereas Dahon indeed built something that is clearly, massively (and maybe shamefully) inspired by the Brompton but also is clearly different in relevant aspects. And typically Dahon it has some chaos in the lineup and a bunch of inconveniences in construction and usage. Interestingly they seem not to be really successful in selling the Curl and definitively not in the price region of the Brompton as they initially tried (and even less as "the better Brompton" as they initially tried as well in a kind of
ridiculous video). But the Curl is the proof that you
can use the form and folding principle of the Brompton legally - if you are different and do not simply copy and clone.
What Brompton does - and I think they are right with that - is to defend their unique shape of the bike as part of the brand and intellectual property. That does not hinder innovations but it stops plain copiers that simply want to profit from Brompton's "fame" and image w/o own innovation. Land Rover did btw. the same in China when Landwind directly cloned the shape and appearance of an earlier version of their Discovery a couple of years ago and succeeded with suing that behaviour even in China. I think (if I remember correctly) even "After Eight" has done the same with products that copied their appearance and were sold at discounters for a cheap price. And all
they have is a square piece of chocolate with mint in it in a dark green packaging.

Since being taken over by Nestle they even have changed their traditional recipe for cheaper, less healthy ingredients to rise profits.
The really interesting thing is that until now nobody has managed to successfully create a folder that folds as good or better than the Brompton and is better in other aspects (be it price, riding or whatever) w/o copying the Brompton. The only one I am aware of who went down a totally new and different approach with a promising outcome is Peter Boutakis with the Helix and he has probably had a very hard time over the last six years, until now still not having managed to build and ship more than about half of the 1.x00 bikes he sold in his campaign at Kickstarter back in 2015. Apart from that a great folder and bike, but not of much practical use in daily life until now. Thus not really a competition or replacement for the Brompton for most people. And not on the cheap side of life as well.