I have the Castle Ravenloft board game. It's basically a slightly simplified version of (4E) D&D. All the powers are basically there, it just gives you what you can do on cards, simplifies initiative. The rules it uses could easily have been part of a "beginners" set of rules for kids.
Like the DM-less version of D&D it's semi-random dungeons using tiles. You use minis, attack, take damage, cast spells, level up, get items and so on. Options are a bit limited, but most of what happens could be implemented as house rules in a normal game if you wanted such as the initiative order where all the players go and then all the monsters/traps go.
There are other D&D board games as well - Murder in Baldur's Gate for example, which is really Betrayal at House on the Hill with D&D characters. But the use of D&D rules is minimal, it's more set dressing.
In the same way that I wouldn't consider a D&D based video game D&D, I don't consider the board game D&D. That doesn't make it any less fun. Which is, last time I checked, the point of playing a game.
So here's the question. Do you consider the Castle Ravenloft D&D? If not, how is it different than what's been described as a DM-less game? If it is, would you consider Murder in Baldur's Gate D&D? Where do you draw the line and why?