The studio was closed. The day 102 meditation discusses Samadhi as being the end for which devotion or surrender to God is the means. I'm not going to minimize the importance that he is putting on this niyama. But there are seven parts to the path of yoga, and most of what I've read points to advancing on each of these limbs at once. If I took Gates seriously here, it might mean that I could give up all the yamas, the other niyamas, asana practice, pranayama, meditation, etc... What's probably closer to the truth, is that at a certain point, each of the practices starts to embody all the others. And that's why it sometimes sounds like Gates is collapsing some aspects into others.
Samadhi is complete union with the object of meditation. In other terms, it is full communion with the devine. Gates notes that many people have a hard time accepting this notion: its simply not compatible with the notion of God they learned as children. His answer is that if you are alienated (which means not in union with) the God of your childhood, then try finding another God. Here's another way to put this, one that does not sound so harsh and heretical: Let's assume that the two notions are truly incompatible with each other. Then, from what I know of yoga, you can still adhere to your old views and take the practical steps that might one day get you to experience Samadhi. If that is all that its cracked up to be, then it must be a pretty good thing on its own. That gives you the best of both: whatever it is that your original faith brings to you, and the benefits of the end/goal of yoga.