Yes, it is. I'm gluten intolerant and I use it all the time for thickening stuff and for making sauces. NO need to use butter then so it's less fattening. (Unless you go mad on grated cheese like I do).
Pearl barley, which I love, is no good for people who can't tolerate gluten unless it's just wheat gluten that it the problem. Unfortunately, I have had to stop using it.