A Golden Great Ape is more or less a regular Great Ape who's turned Super Saiyan. Mastering the Golden Great Ape form is necessary to actually turn into a Super Saiyan 4.

The Great Ape Son Goku, the Aggressor card depicts Goku in a GT- only form: Golden Great Ape. This form is a Saiyan going into the Great Ape, or Oozaru, form and then going Super Saiyan.