I was recently reminded there was a condition inside the GearGen script which tested for Rhino versions and caused the script to stop working on V6. This condition has been removed. The script itself is the same (not a new version). It can be found -> GearGen new location <- under Rhino scripts.
EDIT: The gear limit was also raised to 1000.
NOTE: It came to my attention that a while ago (Varvara Toulkeridou), but together a fantastic tutorial: GearGen tutorial