It may not be glued anymore, and it's easy to find out. It is bolted and in reality that is all it takes to keep it securely in place. There are four bolts which are part of the rubber piece, and the nuts are what secures the spoiler to the trunk lid. The nuts one either end are visible without removing anything. To access the ones toward the middle, you will need to remove the three light assembly underneath the spoiler. (Be gentle when removing this assembly, and take this as an opportunity to clean it.) Once you remove the nuts, you should be able to work the spoiler free with a bit of patience and help of a commercial glue solvent.
Best regards,