Regarding the challenge of helping people understand the distinction between "DITA" and "DITA OT", here are some thoughts stemming from training new (to structured authoring) authors, parts of which some people find a little alarming, but all of which I cling to nerdily and stubbornly nevertheless. It starts with separation of structure and formatting. I use this premise to motivate a pair of diagrams, simple enough that I think you can get them from these verbal descriptions:
1. For "traditional/DTP", there are two blobs in the diagram, one of which says "Authoring tool" and has an arrow pointing to the other, which says "Output".
2. For "structured authoring" the "Authoring tool" blob yields a "Structured document", which sits next to another (originless) blob called "Style sheets". Both of these blobs feed into another one called "Publishing system", which in turn points to the final blob "Output".
The mantra I use with these two diagrams is "With structured authoring you are not creating output; you are creating input." E.g., you are not saying "This stuff should have a box around it and be positioned over that-a-way"; you are only saying "This stuff is a sidebar". Then the publishing system says "Oh yeah, I know what to do with that."
From there it is an easy step to discussing the following very real process, strongly similar to the code-test-debug cycle in programming:
1. Write some code (XML/content).
2. Generate output.
3. Examine the output for correctness.
4. Fix errors and go to step 2.
I talk of the giddy anticipation when you're about to generate output again, the disappointment when it's still broken, and of course that eventual rush when you finally do get it right.
The "fix errors" part is a burden potentially shared by both authors and style sheet developers, which does complicate matters. As far as the analogy goes, this can be handwaved a bit by the fact that we are teaching authors about their particular perspective on this ecosystem. But this also gives an opportunity to discuss the negotiations/compromises that sometimes must be made between markup design, markup usage, and style sheet development effort. (Similar negotiations may occur between product management and development in a programming shop, btw.)
I think you could possibly push this analogy further with comparisons between DITA and programming languages, but I have not needed them, or thought them out enough to be sure how well it would work.
While I admit that this analogy may be a little scary to folks who think programming is intimidating, I also think that it helps strengthen the basic premise of separation of structure from formatting that really is fundamental to understanding why DITA <> DITA OT. The cyclical process with "write code" and "generate output" in different stages reinforces that they are different parts of the system.
mag