Sorry to hear about your friend's accident, Vixen. Here's hoping that the healing will go quickly and without setbacks.

I once saw an employee of a guitar shop playing guitar with the stumps of several partial fingers (3, as I recall), so depending on how much of your friend's ring finger remains, using it for instrument-fingering may still be an option.

If not, he may have to relearn some fingering so that his pinkie finger can do what his ring finger used to do.

Alternatively, he can learn some other styles of playing, such as the one Richie Havens uses (the "barre with alternate tuning" method). Perhaps he could even learn to play left-handed (with the right hand doing the fingering).

Sharon