Not certainly safe though... There are other Sedums that are toxic. Only feed plants you know to be safe. Why feed any succulents that are questionable? Many, if not most desert plants have toxins or spines to protect them.
I've always considered it a weed, I don't know it's name, and I'm not saying to feed it to your tortoises, but it grows wild here in Va and my tortoises eat it when they find it or it gets mixed with their clippings. It has a very small root system, easy to remove if you want it gone.