[cmrdporcupine]

It's not (directly) related to Dutch at all, the "Dutch" thing is just an English spelling of "Dietsch", same word as Deutsch.

The article also seems to mix Mennonite German speakers up with Pennsylvania Dutch speakers, which isn't correct AFAIK.

I think on the whole? Mennonite German ("Plautdietsch") is not the same as Amish (I can't be certain, we don't have Amish here in Canada)... and their language I believe is more closely related to Low Saxon than to Low Frankish (Dutch). So closer to Plattdeutsch in northern Germany. But I also think it has many High German words and pronounciations borrowed-in as well (along with English, and other languages).