The reason Brompton used trademark to sue Dahon Curl is because the look and feel seems like Dahon Curl copied from Brompton. I am not sure about others but it seems to me Curl looks like the MK I, but that bike was discontinued more than 30 years ago. Anyway, just like people here already mentioned, most of Brompton's patents were expired long time ago.

I also pre-ordered a Dahon Curl and about to receive the bike in a week or two. I think it will be like the way it was advertised that it is stiffer and faster than my 6-speed Brompton but probably not as faster as my 2-speed Ti Brompton. I am not a fan of the internal gear hub, particularly made by Sturmey Archer.