Plato and Aristotle got along perfectly well with what many people think was no concept of a separate “will” at all. Aristotle nonetheless developed a nuanced account of deliberation and choice, which should have made it plain for all time that no extravagant assumptions are necessary to provide a basis for morality. All that is required for ethical development is that there be things within our power, not that we can somehow magically escape from all determination.
Curiously, the notion of a “freedom of indifference” emerged in Stoicism, generally thought to be a haven of determinism. The Stoic sage is claimed to be completely indifferent and unaffected by passions, therefore completely free. Some monotheistic theologians applied an even stronger version of this to God. God in this view is absolutely free to do absolutely any arbitrary thing. Some even claimed that because man is in the image of God, man too is supernaturally exempt from any constraint on the will. Descartes thought the physical world was wholly determined, but man’s soul by the grace of God wholly free.
Others thought we are free when we are guided by reason. This view takes different shapes, from that of Aquinas to that of Spinoza.
Kant introduced another kind of freedom, based on taking responsibility. Where I choose to take responsibility, I am free in that sense, with no need for a supernatural power. I can take responsibility for things that are by no means fully within my control. Kant unfortunately confuses the matter by talking about freedom as a novel form of causality, while denying that this makes any gap in Newtonian physical causality.
Hegel too reproduced some voluntarist-sounding rhetoric, but his version of freedom is a combination of both the reason and responsibility views with absence of slavery or oppression. (See also Independence, Freedom.)
Confusion continued into the 20th century notably with Sartre, who claimed that man is free even in prison, and attacked so-called structuralism for allegedly undermining said freedom.
Freedom as reason, freedom as responsibility, freedom as absence of slavery and oppression are all things we should want. As for the rest, see the Appendix to Book 1 of Spinoza’s Ethics (though unfortunately Spinoza is unfair to Aristotle in treating all teleology as supernatural in origin). (See also Subject; God and the Soul; Influence.)
Brandom explicitly mentions theological voluntarism as associated with what he calls the “subordination-obedience model” of normativity.