I would give it to your friend. Most kitty litter is gypsum, which is calcium sulfate. Gypsum can improve certain clay soils which are high in sodium by replacing the sodium with calcium. Such soils are actually rare. You might read over the enclosed link and note especially the following quote:

"The only soil that can be benefitted by adding gypsum is a soil high in sodium, called "sodic soil" or "black alkali." These soils normally are found where there is a high water table and poor drainage. Such soils are hard and cloddy when dry and take water very slowly. Few plants can survive in them."

Here is a link that might be useful: Gypsum and Sodium

It is my understanding that clay is the most common component used in basic inexpensive kitty litter:

http://nydogsworld.com/articles.aspx

I would expect that an unscented, non clumping clay based kitty litter would be useful in a porus soil.

Here is a link that might be useful: components of kitty litter

Kitty Litter is the opposite of perlite. With long exposure to water it becomes soupy clay. Well, there are bound to be other kinds, but I've not encountered gypsum. My package says "calcined [baked] clay." it's usually a type of clay similar to montmillionite, which is very fine and capable of holding great amounts of nutrients and water. If your soil contains less than 10% clay, it is a helpful additive. Dig in a layer of 1" or, if there is no clay at all, 1-1/2".

If it's Hartz Mountain, one of the rose growers up in Virginia has found that brand to be really useful for rooting roses (as its acidity works well with the roses and also tends to suppress molds.)