They make the white whiskey, age it in new charred oak barrels, so there you have your bourbon. After that, they transfer it into the dragons milk barrels for the final aging. As for the legality of it, I'm going to assume it's on the up and up, because everything they do goes through the proper alcohol control channels.
As far as how it tastes, I guess that's all a matter of preference. I've never been much of a whiskey drinker, but I've been getting into it lately. I'm still no connoisseur, but I like it (Beer Barrel Bourbon). It's not my favorite as I tend to lean heavily toward rye whiskeys. I have the Distiller app on my iPhone, and the two New Holland whiskeys on there are both rated in the 60s. In the meantime, there is stuff rated in the 90s that I didn't care for at all.