Documentation and all that now is the job of Google, the best company in the world.
I doubt that Google will want to document any Archos-specific additions to the Java API, even if Archos actually offers any. I'm pretty sure they'll see that as Archos' job.
The Android Java API is already reasonably well documented; but if Archos modifies it (for security purposes, for example) then, again, Archos will have to document it and make potential developers aware.
None of this is rocket science, but it all takes time and costs money.
Archos just needs to take care of customizing the basic Android OS to make it work with Archos specific integration of the Texas Instruments OMAP3440 processor.
Having done some work in this area, I'd be a bit careful about the word `just' there. It's not a trivial job. But it is a do-able job, given time and money.
The hardware API hooks using OMAP3440 features in Android most probably are things even Texas Instruments can work directly with Google to make sure will be working for every part and every speciality of the OMAP3440 platform using third party Android applications.
Maybe -- let's hope so. But, again, previous experience has not been very positive in this respect. TI has so far not published any way to develop for those parts of the OMAP platform other than the ARM code (e.g., video acclerator) except
using their proprietary tools. It's going to cost Google money to get to that stuff, I think. They won't want to do it just for Archos -- whether this works will depend, I guess, on widely the same platform is used by a range of vendors.
The higher resolution large touchscreen, the large hard drive storage, those things could be pretty special and need extra much adaptation work done. I think it is pretty obvious that all of these hardware aspects will be available for third party Android applications to use.
It's not obvious to me. I hope you're right, but it's not obvious.