Sampled material is protected by the same copyright laws that applies to any other recorded material.
Could be a good idea what applies in your country/state.
The choise of michrophone/preamp is very much depending on what kind of sound you like to get. In my experience, the room plays a big part in how the recording will sound.
Take your time trying out different michrophone placements, do test recordings and make test versions of the sampled instrument.
A gran piano is extremly transient and dynamic, so you will need michrophones that can deal with that. Also pay attention to the signal to noise ratio. Remember that when playing a cluster of notes on a sampled piano you are adding up noise since you are triggereing 10, 15 or maybe 20 samples at the same time, buildin up noise.
Also it's a great idea to get a good piano tech to go over the instrument before recording and also to check tuning at lease a couple of times each day.
I hadn't thought about signal to noise building up the more notes you play! I was already going to be very picky about noise, now I am going to be very VERY picky about noise.
I realize this is going to be a major undertaking, so thanks for the suggestions and information. I especially appreciate the fact that you're a sample developer, and you're willing to give me some pointers.
You didn't mention how much studio experience you have, but if you are not accustomed to recording pianos, and you want a really good sound, I would suggest hiring out a good engineer for at least a consultation.
An engineering consultation sounds like a great idea to me, since I don't have a lot of piano recording experience. Maybe some adjusting of the acoustics would be beneficial too, and that's beyond my expertise, such as it is...
Since there are no deadlines to meet I'll probably read whatever's out there about piano recording techniques first (I've seen a number of informative articles in years past), then experiment a bit.
At that point maybe I can cajole Arthur Rubinstein's recording engineer to take a looksee.