it is wrong to pursue sarah while she is still with jake no matter how good of friends they are or arent.
and i f sarah likes joe more than jake then she should dump jake and take some time to get to know joe better and take it slow.
if sarah and joe hook up yeah jake will prbrably be upset but he will get over it or maybe not and joe may loose a friend.
i don think that friends should fight over a girl or guy. i think that the outcome to this depends on how mature joe sarah and jake are. things change and people change its a fact of life.