OK, if having a *not* fully working prototype, and *not* having the thing publicly available means that something isn't to be consider vapor
You have to realize, every product ever goes through this phase.
All products have a period of time where they have working but not complete versions but aren't publically available yet..
Everything..
A product is vapor when it isn't going to be released...
That means that, while there are "questions" about if it will ever be released (assuming the company doesn't say "It's dead Jim"), people have to decide if it is vapor.
In commercial products, this is usually a relatively short timeframe, depending on the complexity of the product.
In these smaller run products, it's trickier still...
One of the main qualifiers for many people is progress..
If there is active news showing progress (albeit slow), most people won't consider it vapor.
Both Natami and FPGAArcade have shown progress recently, and as such are generally not considered vapor.
Now, you could say, as news was slow for a long time, that it was perfectly acceptable to claim Natami WAS vapor, and now is back in development (i.e. Duke 3D Forever)....
It did appear (from the outside) to be stalled, at least until we actually started seeing demo videos of the hardware and it actually working..
IMHO
desiv