Does anyone know what addon that Cirlce addon is?

If you are talking about the compas in the top left cornor, then it's a custom addon or something from the workshop. It's never been on gmodstore at least.

LITERALLY just googling "gmod compass" shows up with this addon as the very first https://garrysmods.org/download/1397/neon-compass

It seems to be exactly the same, the only difference is the color which you can probably change in the lua code.