Place wheat berries in a large bowl and add enough water to cover by 2 inches. Soak at room temperature overnight.
Drain wheat berries and transfer to a medium-size saucepan. Add 3 1/2 cups water. Bring to a boil, then reduce heat to medium and simmer for 45 minutes. Add a little more water, if needed, while cooking.
Drain and cool to room temperature. Meanwhile, in a large bowl, combine apple, dried fruit, celery, scallions and crumbled feta. In a small bowl, whisk together the vinegar, honey mustard, honey and salt and pepper. While whisking, add oil in a thin stream. Add wheat berries and dressing to apple mixture in bowl. Toss gently and serve.