The Renaissance lute (which I used to play, badly) has a "G" tonality, but the tuning intervals are very similar to a guitar, with one exception: the G string is a semi-tone lower. So, using the standard "E" guitar tuning and beginning with the high treble E string and working down in pitch, lute tuning would be the equivalent to: E B F# (instead of G) D A E. On a seven-course lute (remember the highest string will usually be single, not doubled) that's: G D A F C G; and if you have an eight-course lute the next string down (if memory serves) is low D. (Baroque lutes are a different kettle of fish.)

There is a lot of lute music written in tablature, which is quite easy to read and is merely a fingering diagram so it requires no great knowledge of music theory. I mention this because it sounds GREAT on a steel-string acoustic guitar - to my ear the lower pitch and the metal ring of the strings is very exciting; and if you want lute-pitch, just capo to the 3rd fret - though what pitch "G" sounded at in those times is anybody's guess. So, tell your friend to go for it!