Judy and Luke are just friends but they are actors as well. They had love sequences together in their most recent play, but they are merely performing as romantic leads. There was a kissing scene when Andrew was observing Luke's performance. Andrew saw Luke act out a romantic scene and is now confusing Luke's performance with his true feelings. The way Luke acts around Andrew when they are not on stage is likely a truer reflection of his feelings.
andrew says: what are we, are we just friends?
luke says: i dont do *things like this with “just friends”
*THINGS = lovey dovey things (kissing etc etc)
andrew says (as a joke likely): well what about judy
*bc luke and judy have romantic scenes in their play
what did he mean with judy in the start ?