This has to do with the point about agency in the article. Everything in your "light-cone" can and will affect what decisions you make. But there are so many butterflies in your light-cone that you cannot say any one of them (alone) decides what your decision is. They cannot force your decisions and thus you have free will. No other actor can control your decisions. You are free of their will, thus your will is free of their will. Thus you have "free will".