What are the Gods (or the Devil) in your practice of witchcraft? Do they refer to "real" anthropomorphic intelligences, as in the Christian system? Or are they more like symbolic constructs that don't necessarily refer to any single "real" being? I know that some Wiccans basically "believe" in their deities pretty much with the same literalness that Christians believe in Yahweh, but I'm not sure if this is true of your version of withcraft.
The Gods are real beings, able to be communicated with, but are not anthropomorphic. They might take a human form to appear to a human being, but they are unbound by form.
In other comments you refer to "planes of existence" and "spirits", etc. From what tradition does witchcraft get its cosmology?
Whatever religious tradition the witch practices. For me, it's down the raw basics: spirits are disembodied souls, so to speak. Some are powerful, some aren't. Some are so powerful that they might be called Gods. Some are merely ghosts of humans past. I believe in a physical world and the Otherworld, which may be composed of multiple realms. However, as I have no direct experience within that world, I refrain from making that assumption at the moment.
Are there any primary sources used? Not necessarily in the sense of a "holy" book or scripture, but something traditional upon which to base belief and practice.
In terms of religion, no. Before practicing witchcraft, I'd studied Germanic paganism for a while and practiced that according to what I knew. When I transitioned to witchcraft, and later a focus on the Devil rather than the Æsir and Vanir, I took a lot of those influences with me. For instance, my sigil craft mostly uses Elder Futhark to create bind runes, and the same script is my primary crafting language. In terms of witchcraft, apart from religious practices, my influences are varied, ranging from historical texts which cover or focus on the subject, to actual experience from other witches. Most of what I do, however, is trial-and-error based.
How many others are like you and are they organized in any sense? Is it a new movement, if it's a movement at all?
I'm completely solitary, so I have no idea if there are others. I imagine there are those with similar beliefs or practices, but they're probably as happy doing their own thing as I am doing mine.