However, this hook was removed in version 3.0 with no replacement.
No parameters are passed to this event; however, it is useful to note that the GFUser object is a global namespace and properties can be safely added to it from this event.
See Gravity Forms Docs: gform_gfuser_object_init
Adding values to the GFUser object
This example shows how to add two values to the GFUser object and then call another function that processes these new properties.
Since this hook was removed in version 3.0, the provided example and usage are for historical reference only.