Well, no need to jump down his throat about it. Granted, Langerz makes a top-notch kit, but that's no reason a fellow shouldn't try it himself. And should he not succeed, can always buy the actual thing.
I'm not sure, but I don't think all of the parts are off the shelf, so making a copy would be a bit tricky. I'm always in the mindset of "if I can make it, why buy it", but sometimes it's better to keep those thoughts in your head, especially as the creator is a well-known member here. I tried to make my own streetboard and failed, so I'm looking for an actual one.