Light a grill. Grill the pineapple slices over moderate heat until charred on both sides, about 8 minutes. Brush the pound cake with the melted butter and grill over moderate heat until toasted, about 4 minutes.
Cut the pound cake into 1-inch cubes and transfer to a plate. Cut the pineapple into 1-inch cubes and transfer to a separate plate along with the apricots.
In a medium saucepan set on the grill, bring the cream and the bourbon to a simmer. Add both chocolates and the salt and remove from the grill. Let stand for 5 minutes, then whisk until smooth. Serve the fondue with the grilled pound cake and fruit.