From that link, I find that each club is permitted a mix of 500 members (although some had 1000 sign up just last weekend). So existing larger clubs are splitting into smaller subclubs. It also states that they may only sell a maximum of 50grams per month to each user. They may not seek profit. Resale of cannabis from other manufacturers is prohibited, so the clubs need to grow their own canabis! They are also not allowed to hire people to grow, harvest, plant, or even sell in the clubs. It needs to be the members who do this
It's all going to be very interesting to follow, but it looks like there will be a lot of space needed to grow them, and paybe even a lot of energy going to waste on this (instead of growing it places where the weather or even the landscape allows)! Its hard to grow enough cannabis in the center of Berlin I assume