Darl's narration on page 97 of As I Lay Dying is a recursive account of Jewel's cursing rant.
It echoes his only narration on page 14 in which he likewise curses about Cash building the coffin: "and that goddamn adze going one lick less" and against heaven, "it would not be happening with every bastard in the county coming to stare at her because if there is a God what the hell is He for."
It also echoes Darl's narration on page 94 in which Darl continues to psychologically tease Jewel about his mother, "It's not your horse that's dead, Jewel," to which Jewel responds, "Goddmamn you. Godddman you" and, at the end, "Goddamn him. Goddamn him." Later, Jewel with call Darl, "You goddman lying son of a bitch."
So, Darl, being psychic and omniscient with his naturally-born siblings (Dewey Dell), can communicate silently with them. But, because he cannot do the same with Jewel, he knows that Jewel is not his blood brother. Instead, Darl knows that Jewel's a bastard, and he will taunt him verbally (not mentally) every chance he can get, using his mother as bait.
Jewel is indeed a bastard, and like all archetypal bastards, he resents his status in the family. He knows he is dispossessed, and he hates his family, especially Anse (his "step-father") and Darl (his "half-brother"). By cursing so much, it shows not only his hatred of the Bundrens, but also for his mother's death. His cursing is a form of love, a part of Jewel's wild grieving process. Jewel and Vardaman are the only ones who outwardly show anger at her death. Jewel hates that his mother is dead; he hates the journey to Jefferson; he hates having to cross the river; mostly, though, he hates the spectacle of her dead, smelling body. As a sign of his love for his mother, Jewel will later rescue her coffin from Darl's barn burning.
In this section on page 97, Jewel wants to hurry up and get his mother buried. He says, "Pick up! Pick up, goddamn your thick nosed soul" and "Come on. Come on." By contrast, the others want to wait. Cash says, "We better wait." And Anser says, "Steady it a minute, now." Darl says, "Wait, Jewel." So, Jewel fighting with all the other men as they carry the coffin shows the disunity and lack of balance in the family: Jewel is not one of them. He rides alone on horse, not in the wagon with the others. He wishes that this process were over, that his mother were buried already. Jewel hates the public display of the dead. As such, he is like Antigone--the one who risks her life to bury her dead brother; the other Bundrens, then, are like Creon and Ismene--those who mock the dead by public show.
In sum, Jewel's "Goddamn him" refers not only to Anse and Darl, but also to God and even his real father, Whitfield. As a bastard and a mama's boy, Jewel has a definite Oedipal complex in which he subconsciously wants to kill fathers and heavenly fathers.