No they are not the same plant, they're more like sisters...
they both share the same genetics which i believe is haze, northern lights, and skunk 1...but jack herer was selected from a MUCH wider genetic pool and chances are that you couldnt recreate it with 30 different combinations of those three strains.
For me, jack herer had a very open, almost candelabra type growth pattern. it does stretch in flowering but not as much as ssh.
hope this helps. take care.