AMR most likely desires code share to capitalize on JetBlue east coast operations, particularly JFK and BOS and revenue from said code share. Much like Alaska on the west coast who has a code share with AMR. JetBlue has consistantly said they do not want to code share, only INTERLINE with AMR. JetBlue has similar agreements with other International carriers. Interline agreements are common and hardly lead to the Merger/Takeover rumors you alude to.