Hi,
with up to date JMP Versions its very straightforward so this might help others searching for the same thing:
Right Click on the Date Column (date in my case) -> New Formula Column -> Date Time -> Month Abbr.
This would be the jsl code for new formula column:
Substr( Format( :date, "Monddyyyy" ), 1, 3 )
This might not work for JMP 8 but you can try it out.