That guy has another problem. Otherwise the boards would be full of cMP with black screen unflashed cards.
Even if too thrifty to get card an EFI, why not keep a crappy old 2600XT or GT120 around with EFI. The time spent jacking around in that thread would have paid for it.
Thanks Dave, I think it's:
sudo nvram nvda_drv=1
That's what the nVidia Control Panel seems to set.
Everyone else, that's gotten unfleshed cards to work, seems to have used a spare EFI card, as you suggest, and the nVidia Control Panel set the proper nvram variable for them. One other user in the MR nVidia driver mega thread was reporting the same issue of screen sharing not working, and not being able to use their Mac, no video.