If you cook it at home, butterscotch or any other flavor of pudding can be gluten-free, since the most common thickener in home pudding recipes is cornstarch. Check the labels of commercial products to verify the presence or absence of gluten.
Jello is a desert-type food made of gelatin, fruit flavor, and coloring. Pudding is a desert related to egg custard that is made of sugar and milk and is thickened with gelatin or corn starch. Jello tastes a lot better than pudding.