Seth Lipsky argues that Lincoln, and FDR as well, would have pretty much tried to hang the Wikileaks founder for treason:

It is fearsome to think of what kind of black rage it would have put Lincoln in. He nearly brought Horace Greeley up for treason just for trying, as the famed editor of the New York Tribune did, to arrange peace talks with the South. Imagine if the oleaginous Greeley had been, while in foreign and even neutral countries, publishing tens of thousands of sensitive telegrams naming our agents, and our units, and disclosing to the Confederacy what we knew and when we knew it. Can one even conjure the intensity of his anger as he sat, as one can imagine, in Secretary of War Stanton's cavernous office, poring over the details of the breach as an aide read out the sanguinary consequences?

Same with FDR. He was in a fury at the Chicago Tribune, and the Tribune was a patriotic paper. It did publish stories that, en passant, made it known that we had broken the Japanese code. But its purpose was not to destroy our war effort. It was a breach en passant. Yet FDR, as Conrad Black puts it in his biography, "Champion of Freedom," "exploded" and ordered the secretary of the navy, William Knox, "to send marines to occupy the Tribune Tower." Knox, himself an ex-newspaperman, dodged the order, while Roosevelt tried, albeit unsuccessfully, to get his attorney general to charge the proprietor of the Tribune, Colonel McCormick, with treason.

UPDATE: Yes, I know that Julian Assange is not an American citizen (though his source, and some of his collaborators, are). The much better way for me to have characterized Seth Lipsky's provocative editorial is that he believes Assange should be treated as an enemy combatant and his American collaborators be tried for treason, though he's obviously arguing that Lincoln and FDR would have dealt with American versions of Assange very harshly. In some ways, the real target of Lipsky's ire is Brad Manning, the American soldier who apparently leaked the material to Assange.