i have that Module and i can see the Category Tab in the Backend.
For my Use i have a Board called "Kickertische" and Categories named "Lehmacher, Fireball, etc." but none of these are showing up in the Forum.
Only the "Kickertische".
well i have a similar issue here - i have (rather i plan to have) multiple forums including subcategories. http://test30.rfa.ch
First problem i encounter is that all my forums see the same category
second as i was looking at your forum, you are using the categories and adding the forums in a nice order which i should be able to accomplish with numbers but that don't seem to work for me. would like to have it (or similar) as my old page http://e.rfa.ch