NDP is short for 'non-distiller producer.' The designation is self-explanatory. Some producers make what they sell, starting with the raw materials of grains, water, yeast, and charred oak barrels. They mill, cook, ferment, distill, age, and ultimately bottle the product, put one of their own names on it, and sell it through their own distribution channels.
Other producers buy aged whiskey in bulk from one of the distillers, either directly or indirectly through a broker. Then they bottle and market it. Those are NDPs.
You can't tell distillers from NDPs by reading the product label. You more-or-less have to know. This isn't as hard as it sounds because the number of distillers is small, especially if you exclude micro-distillers (who rarely sell in bulk). Virtually all of America's whiskey is made at 13 distilleries owned by eight companies. All of the NDP whiskey is made by those producers too.
Most distillers market their whiskey under multiple names. Some produce a handful of brands, others dozens, but they're not a secret. Some make a couple of different recipes and matching recipes to brands takes a little more research but that's not a secret either. The companies are usually upfront about it on their web sites.
The Maker's Mark Distillery, which is owned by Beam Inc., makes Maker's Mark bourbon and nothing else, no other brands. The Jack Daniel's, Woodford Reserve, and George Dickel distilleries likewise make only their namesake brands in a couple of different expressions. Everybody else makes multiple brands. Jim Beam, for example, makes Jim Beam bourbon and Jim Beam Rye, but also Knob Creek, Booker's, Baker's, Basil Hayden's, Old Grand-Dad, Old Crow, Old Overholt, and a couple more.
MGP of Indiana is included among the distiller producers, although they make no brands of their own. However, most of the NDPs who use MGP whiskey identify it as the source.
That brings us to the NDPs who keep the source or sources of their whiskey a deep, dark secret. Templeton Rye, for instance, would like you to think its product is made at a little distillery in Templeton, Iowa, when it's actually made at a great big distillery in Lawrenceburg, Indiana.
Templeton is not unique. Some other NDPs you may know are Michter's, KBD (Willett), Black Maple Hill, Whistle Pig, Jefferson's, Pogue, and Angel's Envy. They make nothing themselves. Because most of their products are quite good, there is always a lot of speculation about who made this or that expression.
You are of course free to buy whatever you want and equally free to speculate about the provenance but consider this: why do business with someone who makes you play stupid guessing games about the basic question of who made their product?
"Because I like it and don't care who made it," is a fair answer.
There used to be a lot of bulk whiskey around that was made by closed distilleries, but virtually all of that juice is gone. All of the NDP whiskey you get today was made at one of those 13 distilleries by one of those eight companies. With the exception of MGP, it was made by someone who also sells that same whiskey (more-or-less) under their own names. When a distillery makes a bulk whiskey sale, do you think they deliver their best whiskey? Of course not, their best whiskey goes into the products they put their name on.
NDPs are secretive because they want you to believe they made the product themselves and some go to great lengths to create that illusion. They rarely lie but will spin like dervishes. When pressed, they claim they're contractually prevented from revealing their sources. Maybe they are, or maybe that's just a convenient excuse to continue the deception.
Look at it this way. You can get plenty of good whiskey from companies that don't try to deceive you at every turn. Do business with them.
ADDED A FEW HOURS LATER: Here's a good example of how NDPs hurt themselves with their dissembling. After this went up, a poster in a discussion group where I linked to it took great offense at it. She felt I was insulting her friends who work for the companies I named. She got very upset with me and called me many names, but who do you think she'll be mad at if she eventually learns that everything I wrote is true and what they told her is a big load of crap? And she's a bar manager, their customer.