The whole "it's not really D&D" meme is such a waste of time and energy. Because it doesn't matter if something is or is not D&D. If you enjoy playing it, that's all that matters.
Agreed.
But we note that this is an edit to a post that includes "they don't bear the official D&D brand name, thus they aren't D&D".
I am not sure exactly what "D&D" means, apart from the obvious trademark and brand issues. However, I would strongly hesitate to allow general identity to be determined by trademark and branding.
When I was younger, we (and this "we" refers to myself & my gaming friends at the time) never called Villians & Vigillantes or Gamma World "D&D". They were seperate entities, and we knew what we meant when we referred to them. When one of my friends branched out into Tunnels & Trolls, and another into Warhammer, we called each of these things by their own names.
"D&D" (the brand), to me, ceases to be D&D (the entity) when it loses too much of its Gygaxian flavour. YMMV, and probably does. LL, OSRIC, and Basic Fantasy (for example) have that flavour in spades, and thus seem a lot closer to what "D&D" is to me.
This isn't a statement as to the relative value of various game systems -- although I don't think 1e Gamma World is D&D, I do think it is an enjoyable game, for example. It's just my opinion.
RC