The frame builder maybe subcontractors to Dahon and Tern and Crius. Some of the frames may be sold in big enough quantities that the builder will give them an exclusive on the design. Like the Dahon Speed frame and the Dahon Mu frame.

The inner workings of companies can be convoluted. Sometimes the left hand is doing the exact opposite of the right hand.

An example of different directions is the Ford Dahons. Bikes contracted through Dahon and licensed by Ford to sell in the US. I don't get why either Ford or Dahon would authorize another company to sell bicycles of low quality with their name on them.

The contracting out of all the work to build a bicycle has huge risks. Schwinn had Giant building almost all of their bikes. Schwinn gets in financial difficulty and Giant starts selling bikes under their own name---especially targeting Schwinn dealers.

I don't know if Dahon is building their own frames and assembling them or if they are more just the designers and they have subcontractors build the bikes.