freindship

If it doesnt offend the wife maybe. but its kind of asking for trouble

depends on how you put it.You can be friends with also letting his wife know that you are friends and nothing more.You know that platonic friendship.It 'll mean that there is nothing going on between you two,you just have that true friendship.And then again maybe you can be friends but decide to keep it dow low,but that would look suspicious,dont you think???