It will be permanent, I imagine, to avoid collisions at sea. The farm was built outside of shipping lanes, radar areas, birs migratory paths, pipelines; etc..., so that area was not used in anyway. Now it is used and thus has its buffer zone on the maps. In practice it should not change much.
Does this exclude all comercial fishing as well?  What does the opperator pay for the use of the sea area?  I'm curious to know if such developments might be good for the fish stocks.
Horns Rev in Denmark has been good for fish stocks.