As in morally good?
good in any sense really
It seems to me that "you are good" and "you are well" are synonyms here, wouldn't they be?
"You are good" (you are a good person) is almost the same as "You are well" (you FEEL good / you are healthy) - but not QUITE ;)
Are there particular rules for the "th" sound? Tha is "ha" but thu is "oo" and despite it sounding funny, I would've initially guessed thu would also be "hu"