Boozy Concord-Grape Ice Pops

Toast juniper berries in a dry small skillet over medium heat, tossing often, until fragrant and skins are very glossy, about 1 minute. Let cool slightly, then crush with a mortar and pestle (or place in a resealable plastic bag and crush with a rolling pin). Transfer berries to a small saucepan. Add sugar and 1/4 cup water and bring to a simmer, stirring to dissolve sugar. Remove from heat and let sit 30 minutes. Strain juniper syrup through a fine-mesh sieve into a small bowl; discard solids. Place bowl in a bowl of ice water and let juniper syrup sit, stirring occasionally, until cold, about 30 minutes.
Stir juniper syrup, grape juice, gin, and lime juice in a large measuring glass or a medium pitcher; taste and add more lime juice if needed. Divide mixture among ice-pop molds and freeze until liquid is beginning to crystallize, about 1 hour. Cover and insert sticks (waiting until liquid is slushy ensures straight sticks), then freeze ice pops until solid, at least 4 hours but preferably overnight. Dip molds briefly in hot water to release pops.
Ice pops can be made 1 week ahead. Keep frozen.