I have a BDS 2" lift and I did a lot of web searching and I found there were not many discounting their products. Most of the prices were the same including ebay. I found one vendor that had a holliday coupon active on their web site (way past christmas) and an error in their shipping calculator. All of which made it a slightly cheaper deal. (I ended up splitting the shipping cost). Google is your friend, so shop around and see what you find.
With regards to the warranty, read what's on their site (it's there). Unless it specifys "AUTHORIZED DEALER" which I don't believe it does, you are fine.
2003 TJ, 33" BFG AT, 2" BL, 2" BDS spring lift, Truck Lite headlights, Homemade sunrider top.