You might very well have purchased it because it's billed as "the toughest glue on planet earth." And after you've spotted some dried Gorilla Glue residue on a piece of glass, you know the manufacturer wasn't monkeying around with marketing platitudes. Removing the residue requires patience and probably some repetition -- consider it a good thing to know this upfront, so the probable recursive nature of this task doesn't cause you to go bananas.
Use the Right Tools
Size up the challenge before you. Gorilla Glue is waterproof. Also, the manufacturer recommends that cured glue "be removed with a chisel, scraper or sandpaper." Given the force created by the first tool and the abrasive quality of the third one, it's best to choose a sturdy plastic scraper to remove the glue from glass.
Proceed With Caution
Put on a thick pair of work gloves and position yourself so you can get a good grip on the glass while wedging the scraper underneath the glue residue. Pry at the glue to lift it and remove it. If you cannot make any discernible headway in one spot, move the scraper slightly. Continue moving the scraper in a 360-degree circular direction -- all around the glue spot -- until you can successfully lift it and remove it from the glass.
Clean the glass with what is arguably the most effective, non-streaking glass cleaner of all: vinegar and water. Mix a 50-50 solution in a spray bottle and squirt some on the glass. Wipe the glass clean with a paper towel.