Now, 8 years later, I have to say that hardly no one wants to pay the IT costs for the catalogue. Since I don't want to ask any more, here's an official statement: The catalog is free for you, I'll continue to bear the anual costs of 720€ almost entirely myself.
However, I would appreciate it if you would send me some stickers from time to time as a thank you. That way you can get the 'Premium Membership' with a lot of additional content like magazines, statistics, galleries and insights.
Have fun everyone