No there is no documentation.
Technically... DynamicComponents is a Google/Trimble extension. And it is not OpenSource.
Practically... it works (and is thought of,) as part of the Sketchup application itself. (The fact that it's written in Ruby, raises some stability issues if a lot of people began messing with it. And.. also, it would run alot faster if it was re-written in C/C++.)
What you may not have realized.. is that DC are really just Sketchup::ComponentInstance instances, that have specially named attribute dictionaries and attributes, that are used by the extension, to do nifty things.
Because it is an authored extension, it's internal workings are subject to change. Even it's internal methods could change their names, but externally, end-users, and scripters, might interact with them in the same way (or without much change.)
So, much of what we know, has come from little tidbits, revealed by the members of the SU Dev team, .. and we can assume, that they have told "the world", what they are comfortable revealing.
Or.. it may be that Google was never willing to spend the money, to produce the documentation.
Or perhaps.. maybe the Ruby version V1 is the proof of concept... and they always had hopes of "baking it into" the C-side API code. (But just have never had that phase percolate to the top of the "to do" list.) Anyway.. if that happens, who knows what the method names exposed to Ruby might be ??
This latter possibility, is the reason I never attempted (even though I thought about it,) to write a reference manual for DCs myself. (That and I would imagine, they would have to give their "blessing" for it. I'd never do something like that without asking. Wouldn't like it if someone did it to my closed source work, without permission.)
