Download the zip and do not unpack it. In Blender open Edit > Preferences > Add-ons, click the drop-down arrow in the top-right corner and choose Install from Disk, then pick the zip. Tick the checkbox next to ColliderKit. Press N in the 3D Viewport and open the ColliderKit tab.

Blender 4.2 LTS and newer. The README inside the zip records tests on 4.2.9 and 5.2.0. ColliderKit is pure Python with no compiled binaries and no external Python packages.

Pick the Engine in the Shape Generation panel and the collider gets that engine's naming:

Unreal Engine: UBX_ for boxes, USP_ for spheres, UCP_ for capsules and UCX_ for convex hulls and decimated meshes, the prefixes Unreal's FBX importer reads as collision.
Unity: a child mesh named _col; Unity has no import convention for this, so you attach a Mesh Collider to it after import.
Godot 4: a mesh named -col, Godot's collision import hint.

Colliders are also gathered into a Unity_Colliders, Unreal_Colliders or Godot_Colliders collection when Group in Collection is on.

Box, Sphere, Capsule, Convex Hull and Decimated Mesh. All of them are built from the evaluated mesh, so Subdivision, Mirror and shape keys are taken into account. On an empty or degenerate mesh the add-on skips the object with a warning instead of producing a zero-size collider.

Yes. Add Compound Shape stacks several primitives on one source; they are numbered automatically (for Unreal, UCX_Name_01, UCX_Name_02 and so on), and Merge Compound to Single Hull turns them back into one convex hull. For a concave mesh, the Convex Decomposition panel splits it into up to Max Hulls convex pieces (2 to 16) by cutting along the mesh's principal axis; Volume Threshold drops hulls smaller than the chosen fraction of the total volume.

Turn on Mirror Collider and pick the Mirror Axis (X, Y or Z) before you generate. ColliderKit writes a mirrored copy of the collider with engine-correct naming; the mirror is baked into the mesh and its normals are recalculated so they face outward.

No. The add-on contains no network code; everything happens inside your Blender scene.

Yes. The add-on is GPL-3.0 (full text in the LICENSE file inside the zip). The license covers the add-on code; the colliders you generate are yours to ship in any project. The full guide is in the Documentation & FAQ tab on this product page, and README.md inside the zip covers install and quick start.