Ghee is simply clarified butter. Pure animal fat, with the milk solids removed, and as such, it is something I feel entirely comfortable using as part of a paleo diet.
There are qualitative differences in grain and grass fed beef, and I’ve only found one source for organic grass-fed Ghee.
Pure Indian Foods sells organic, grass fed Ghee via mail order. I usually keep a fair amount on hand (since it is only made in the spring and fall, when the cattle can graze).