the forwarder channel on WiiU side is a modified vWii launcher channel.
The official one is doing this : launch vWii, then load the TitleID("system menu") located on vWii's NAND.
The USBLoaderGX channel is doing this : Launch vWii, then laod the TitleID("USBLoaderGX forwarder") located on vWii's NAND.
The "USBLoaderGX forwarder" channel still need to be present on your vWii.
It's the one responsible for loading the "boot.dol" located on SD:/apps/usbloader_gx/ folder.
This is what this thread is about.
There is a direct WiiU forwarder channel to load the SD's boot.dol, but the way it works it blocks a lot of features :
you can't reload to another cIOS (no d2x cIOS 249)
you can't use USB
you can't play wii games
you can't play wiiware or virtual consoles on emuNAND
But it allows you to:
Use WiiU gamepad in games!
use it to launch nintendont with games located on SD card.
And MAYBE (untested! or buggy) launch wiiware or virtual console on NAND.
This is
that other thread you need to follow if you want this second version.