Each Jedi costs 1 less build point to deploy. A Jedi Character can have more than 4 cards in its stack.
This Location essentially turns off the "a stack can have at most 4 cards in it" rule for all Jedi Characters (yours and your opponent's), no matter whether in an arena or the build zone.
If Jedi Temple is removed from play while you have more cards in a stack than the rules allow, the stack can remain, but you can no longer add to it.