Advertising is free! There are no hidden costs or commissions.
We are hoping to finance this site with external advertising (banners and so on). It may be that at some point in time we will have to start asking a fee for advertising, but rest assured! If this happens we will inform advertisers well in advance so they can opt out if they want, and we will create discounts for the ones that have been advertising with us from the start.
For now just place your ads without any worries, you are not bound to anything.