exactly, if you (or others) are experienced with GigaStudio you could
try to assemble a .GIG instrument.
Basically you just download the .aiff files, convert them to WAV (I
guess GS cannot read .aiff)
and edit them (mainly trimming silence at the beginning, at least one
sample as far I remember,
has a a few wrong samplepoints in it which cause a bit of distortion,
but I guess you can fix it
easily with a sample editor).
Then create a new instrument, load the file into GS and map them on each
(3 samples (pp,mf,ff) per key).
At that point the instrument is ready. The only thing you need to tune
at that point is the
velocity splitting eg. how to divide the 0-127 velocity space in 3 parts.
I don't know if this velocity optimization has to be done once per key
(probably to get best results you need to do it on a per key basis).
I would advise you to play the Chopin MIDI file on the piano comparison
page and see if the velocity
mapping sounds convincing.