I have the book. It says, and I quote, "Say these words, Nades, Suradis, Maniner. Know that you are summoning spirits of lust. Chant the words two more times…
Chant the following words, Sader, Prostas, Salaster. Speak directly to these spirits of lust, with authority while picturing lustful situations."
Nowhere does it say these words are the actual names of spirits of lust, only that by chanting the words you are summoning such spirits.
Now, in the Black Pullet, where these words come from, it says to whisper “O, Nades,Suradis, Manier” (once he does, the author describes a spirit with rose coloured wings appearing before him, kneeling, and his teacher tells him that the spirit awaits his orders). Then the author is told to say to him, “Sader, Prostas, Salaster,” and the spirit disappeared, to “fetch the most beautiful of human forms.”
So Sader, Prostas and Salaster, are command words, NOT spirit names. The spirits are nameless. The first set of words summons them, and the second set of words commands them.
And to answer your other question, the spirits are basically a type of elemental, as the author of the Black Pullet describes four classes of spirits, but they are not identified as any specific species name like angels or demons, only as “the perfect beings whom the common herd adore and reside in the stars; those of the spirits properly called with which we have conversed; those beings less perfect, but who render great service to humanity; those of our souls who have been separated from their body.”
The spirits summoned by the command words fall into the second classification.
Oh, and the Gallery of Magick specifically states in their FAQ that the spirits are not Djinn, but angelic and elemental: