Of course no fee, fee will be counted only if the orders filled!
Then nothing refrains people/companies from placing and removing thousands of orders per second?
Exchanges could also charge for that.
They could charge for that, but that would simply drive people away to other exchanges that don't. Traditional exchanges and brokers usually don't charge for unfilled orders either.
Note that this is also the reason why you should largely ignore buy and sell walls and why market depth can hardly be trusted.