Yathosho is right, I forgot not everybody allows it.
Tip - dump 2.82 and switch back to 2.81d. 2.82 is buggy. You can download it here
The AVS studio itself is free to use, as I stated earlier. There is no other documentation (that I know of).
The individual presets (including those that were bundled with winamp) may not be, unless stated otherwise.