Maybe we are not on that list because you are in Germany and our website is in english? 
Most if not all of the products listed on that page are in Germany or have German websites. We have a bigger presence in the United States and in other english speaking countries, though our software is localized and used in German and many more languages.
I’d also be interested in hearing more stories from people here on meta who use Discourse for internal community, and how it is working out for them. We ourselves have always used discourse internally, as @HAWK wrote up in a blog post a while back.