Normative decision theory is basically the theory of decision under uncertainty, that gives us one possibly safe way to go from unwanted mental states to more stables and reliables mental states about the world. The objective? Control. The purpose? ... a better performance in the art of survival.
As well as survival is an art, so it is Computer Science, where the way to get the result is not so important as the result itself. And the result is : can be anyone (involved in the matter) understand it, and use it? Art, is after all, a matter of communication.
If I have to evaluate DDT and DATA, then I would do it from the point of view stated above.
DDT is about teaching decision theory. The very well used body of knowledge (probability theory and linear/bilinear programming), supports the principles behind the DELTA method. There is no mistery involved in the explanation; although the lack of simple, and small examples showed on the book (Computational Decision Analysis). DDT, which is the computer tool that implements the method, is actually a not so friendly interface. Is true that it has a graphic interface, but (and this is the view point of an experienced programmer and user of systems) you don't get a fast grasp of the situtation the first time you face it. But, like I set, DDT is just about teaching decision theory.
DATA is about using decision theory. DATA, on the contrary, is easy to use, to understand, powerful in its functionality, and (very important) the results can be communicated beyond the borders of the system, using OLE technology. The manual use simple examples and solve them as if the user came from the kindergarden. DATA is about guiding stupids, so the manual or references to the tool, merely explain the mathematical principles behind.
The way I see it, is that DDT and DATA have, from the very beginning, different objectives. DATA reaches the heart of the market, and DDT the brain of the students.