1. Remove stems from fruit. Rinse and pat dry with paper towels. Place fruit in a 4-quart saucepan over medium-high heat. Add grape juice and honey; bring to a boil. Reduce heat to medium; simmer 15 minutes, stirring occasionally. Remove from heat; let stand 10 minutes. Place blueberry mixture in a food processor; process until almost smooth. Strain; discard solids. Chill 2 hours.
2. Stir in rind, juice, and salt. Ladle about 1/2 cup into each of 5 chilled bowls; garnish with mint and additional lemon rind, if desired.