I finally gave up on the Dahon Reecharge. It may well end up being a good project, but the delayed release is getting too close to my departure. Last I heard was sometime in June, but it wasn't known if that meant early or late June, and I'm leaving at the end of June.
So, I ordered an E-Werk from StarBike in Germany (along with a B&M Cyo headlight and a B&M Topline taillight). The combined price, with shipping, was ~$250 USD. I would have preferred to buy everything in the U.S., but that would have cost another hundred or so bucks..
Initially I didn't want the E-Werk because it doesn't come with a battery, but then I remembered that I already have a battery that can be charged by and deliver power through USB. (BTW: you can get such a battery very cheaply). So, ultimately, I think the E-Werk will be more versatile, and it will be easier to replace the battery as necessary.
Anyway, I don't expect the E-Werk to arrive for another week or so, but I'll post back when I get it.