I'd like to share my theology on this subject:
Imagine a world in which almost all of the humans are animists and polytheists. Including the Canaanites. This people have a two tiered society of god-kings and peasants. The peasants revolt and many vacate the district, causing the collapse of the Canaanite society. Eventually the area starts to grow again as many who drifted away, start to drift back again. They create new groups that form new identities, new tribes... including the Jews.
As eager as any new tribe to set itself apart, they forge their own identity, new stories (including a story about being outsiders who were given Canaan by their god). This god (YHWH) they picked up in their travels (I've heard they got him from a small north African tribe). They became, as Jews, a henotheistic (belief in many gods, but DEVOTED to one <tribal> god) tribe. Supposed to only actively serve YHWH, but forever getting into trouble for worshiping other deities and spirits.
One of these other deities/spirits was Azazel. Apparently a Goat God/Spirit, Azazel seems to have represented the 'God of Out There'. An outlaw in the truest sense of the word. Those who are outside of the laws, requirements, protection of tribal identity. Not necessarily criminal as often thought in the modern world. Indeed, it was quite common in the old world to have a situation where city states only guaranteed protection to their own citizens or allies. Anyone caught outside those boundaries might be taken as slaves. Consider the sanctuary of the Goddess Diana and her role as Goddess of outlaws, and how she preferred to live beyond the boundaries.
So back to the Jews. They were promised prosperity and freedom if they were faithful to YHWH. Archaeological evidence, and biblical accounts, show that they weren't faithful. So when they were dunked and enslaved by the Babylonians, they did the 'poor us, why did it happen?' questions, and came up with the correct answer. 'We weren't faithful'. After 70 years, they regained their freedom, and returned to Jerusalem, full of resolve.
With one small difference...
While slaves, they had enough exposure to Persian Zoroastrians to see how well the Zoroastrian doctrines of moral accountability and the good god/ evil demon would fit their own needs. So the birth of 'One Jewish God and an opposition' was the new way of Israel.
But who could be this new Satan?
Actually, to address the old Satan and Lucifer: the angel by that name in the book of Job, was a servant of YHWH, fulfilling a purpose in accord with YHWHs will, and not the Satan that we generally think of these days. Lucifer was a Latin translation for an earthly king, that YHWH claims to have given the opportunity to rule, but turned out to be corrupt, and was brought down by YHWH.
Anyhoo, back to the new Satan. Well, for as long as there was a Jewish identity, up until the Babylonian captivity, the Jews were worshiping many deities. And then they find themselves deposed by YHWH and his priesthood. And YHWH declares that he has an opposition.
I suggest that given the nature of Azazel, and that he seems to be the focus of one half of a ritual mentioned in the old testament in which one goat is symbolically loaded with the sins of the tribe and released into the wilds, and that modern images of Satan depict him as having goat features, that in all likelihood, Azazel is Satan as leader of the old gods in opposition to YHWHs claim to sole-soul ruler.
Meanwhile, the Jews had a theological problem. THEIR god was now the ONLY god. So, what was his plan or relationship with the rest of humanity? Many 'prophets' had a go at answering that question, but Jesus had the greatest success. His followers spread via the underground, until Constantine the (so-called) Great made it the official religion of the Roman Empire. Then it really took off. The religions of the world declined wherever this pestilence spread, and the old gods receded into the background while YHWH ruled the airways.
And where was Satan based? Might it be too much to suppose that while YHWH set himself up on the throne of Rome, that Satan might be walking the streets or forests? That he might be making alliances with the local gods, to fight the forces of YHWH?
Indeed, I think such an idea might go a long way to explaining The Gospel of Aradia. Diana and Azazel, similar natures. Diana had previously loved a person that might have been a horned deity, so memories might have been stirred. As for the deity in the Gospel being referred to as Lucifer... so what? They didn't have access to the internet or the information we have now. They would have evolved their own myths from available folk law, and they don't seem to have been the only ones to have drawn the comparison. It's common even now. It's common now, even for those who make the distinction, to think of a gnostic deity, to be who was referred to in the bible, instead of a human king. Stuff gets muddled. That's life.
Another example if the whole 'Jesus' birth and nativity scene' thing. Most people picture three wise men standing over the manger in the barn. But actually read the bible, and lean that they arrived a couple of years later (travel time) when Jesus was a toddler living at home. That's why the order was given to kill off all the male children three years and under. Why do we get the idea that it all happened around the manger? Poetic license. It was easier to put on a play with fewer props and scene changes, to do it as one set. So we get a picture. Doesn't matter much.
I expect that many traditional witches, over the centuries, acknowledged Satan as a primary deity, or YHWH, as well as other deities, or no particular deity at all.
And on to modern times. Without thousands of years in the open, Satanism has been sporadic and isolated, so they haven't developed orthodox theology. The last couple of hundred years, as Christianity has lost some of its strength, various individuals and small groups have made a go of Satanism. But still there is no single orthodoxy.
Personally, I have an animist and polytheist view of spirituality and religion. I think Satan is a name given to Azazel, and Azazel was a mid-east deity of a species type that might include Cernunnos, Pan, Frey, and Exu.
On the subject of names. Pick the name of any deity that you like and can relate to a specific culture. What was that deity' name, 40 000 years before that culture existed? This exercise doesn't apply to atheists or those who believe that deities are only as old as their believers. My point is that the deity probably has a name from before there were humans, and any names we give them are just useful tags for establishing communion between species. So 'Satan' is as valid a name as any. Just so long as it's attached to who you want it to be attached to.
And there might be more communions and more names than deities. i.e. double-ups. So Azazel might actually be Satan, and Acteon, and Lucifer, and Herne. This does not suggest that 'all gods are one god', but rather 'a thousand gods might be a hundred gods'.
Interesting musings and insights, voted this up...