I'd be more irritated at the "The Zegul Baidarka really has very little in common with the original baidarkas" bit. If Nick says he deviated from the baidarkas in design, but kept most of the characteristics of a baidarka, I'm comfortable with that. If Zegul took his design, altered/improved/butchered it further, and deviated so much from the original design that it no longer shares most of the characteristics that define a baidarka as a baidarka, then they're wrong.

Fortunately, the sea kayaking community is fairly small, and fairly educated. Word gets around small communities quickly, too.

I'd look at Nick's design, and go "Ok, I can see where he says it's inspired by a baidarka. In fact, it's got most/all of the characteristics I'd define as a baidarka, so let's call it one."

Zegul's? Nuh huh. I'd look at that and go "Baidarka? Really? No bifurcated bow (or similarly shaped); smooth pointed stern. That's not a baidarka. If they're gonna call a boat something that it's clearly not, do I really want to buy a 'yak from these folk? Nope." I may not know much about kayaks in general, and baidarkas specifically, but their "design statement" points out characteristics that aren't in the design. I don't believe that depression in the bow qualifies as a bifurcation. The photo in the review seems to emphasize it, but it looks minimized in the cross sections. That stern is not of a baidarka, either.

The plagiarized paragraphs? I'd spend a few bucks on a lawyer to send a nice polite letter pointing out the similarities, and request they change their plagiarizing ways. Suing overseas is probably more trouble than it's worth, though, so I'd wouldn't put too much money into that lawyer.