In a medium pot, heat 1 tablespoon oil over medium heat. Add couscous and a dash salt; sauté until most of couscous is golden brown, about 3 minutes. Add the vegetable stock, increase heat, and bring to boil. Reduce heat to medium-low, cover, and simmer until liquid is absorbed and couscous is tender, about 10 minutes, adding more broth by tablespoonfuls if too dry. Transfer to a large bowl to cool.
In a small bowl, whisk together the lemon juice, mustard, honey, pepper, and 1/4 teaspoon salt. Gradually whisk in oil, whisking until combined.
Once couscous is cool, combine with the cherries, apples, and walnuts. Pour dressing over mixture; toss to coat. Divide among individual plates and serve.