I wouldn't use it to stretch grain, simply because at 9% protein it will drop your protein content and therefore drop production (IE, eggs, milk from goats, growth from goats) along with it.
I have it in my mix. At the farmer's market last week, I had someone come looking for chickens fed a corn free diet. It is not the worst thing out there (most don't want soybeans in the diet), and I told him how unsure I was that I'd ever take corn out of the diet.
I offer corn as the energy source as well as the 'hot' feed in wintertime. Both of which are necessary, IMO... They just don't get good, quick energy from other food sources.
My mix has soybean meal, oats, corn, alfalfa meal, and a mineral mix, all finely ground and mixed well. It's an 18% mix and all the ducks and chickens get the same mix, except for broilers and turkeys which get the same mix, higher soybean content to get it to 25% protein. Layers get oyster shell on the side free choice. They also free range and in winter have access to hay from the goats. They seem to like it, I get good growth, and I've been very pleased with it.