If you do not use glue OR set screws and whatever you attach to it does not have sufficient weight to ensure no one can lift it or make it jump up, it will come off. In essence, the Hovr bracket system is a supercharged french cleat, and still needs to be secured one way or another.
You can learn more about the set screws in the following articles:
Do I need to use set screws?
Do I always need to use the same size of set screws?
How to make set screw holes and taps
Or you can learn more about how to glue the aluminum Hovr bracket system below:
Can I glue the male and female brackets together? How?
How to glue aluminum