You buddies 05 LLY can be tuned with either FlashScan V1 or V2.
If you are assisting him, my suggestion would be that you/he orders a ne BLUE FlashScan V2, not a black unit. That way when we release support for your 2003 you won't need to purchase another tuner, just use the one FlashScan device for both the 05 LLY and the 03 5.9L.
The Black FlashScan V2 doesn't support SCI communications as used on the 03-05 Cummins, however the new black FlashScan V2 unit does.
All that said, there are some license activation costs to tune both GM and Cummins, but overall it's a cheaper option than purchasing 2 pieces of hardware if that's the path you wish to travel.
If you have no intention of tuning your 03, then your buddy should know that FlashScan V1 will provide the exact same tuning results as the FlashScan V2, although the V1 doesn't have all the bells and whistles that the V2 has (ie. limited licenses, limited to pre CAN GM only, needs to be connected to a PC for reading/flashing, logging limited to 25 mins)
Cheers
Cindy