There are currently both.
FLAK units - FLAK18 on axis side, Bofors on Allied side.
FLAK script is running for both sides and is bound to these units.
The reason there is also a flak script and also real FLAK units is because the FLAK units currently don't or barely show explosions in the sky like the real guns we are used to see in old pictures/videos. Therefore, the FLAK script is here to compliment to this gap.
Notice that if the FLAK units are destroyed, there will no longer be FLAK shots in the area from that objective.