Please take a look at the official Plugin Writing Guide
Most likely the theme will need some integration before subcategories will be shown. At present, I believe only vanilla and lavender show subcategories.
The official plugin is the one maintained by the NodeBB team 🙂
Other forks might add additional functionality or fixes, but it's up to the user who forked it to make sure the changes are transmitted upstream
Plugin updated for 0.6.x of NodeBB.
0.1.1 for 0.5.x
0.2.0 for 0.6.x
Don't confuse the two. 👍
@julian I found the category notifications plugin earlier today and I think it's going to be quite useful for our users so I'm glad that it exists!
Contest has started, here's the official link: https://community.nodebb.org/topic/2527/nodebb-plugin-theme-contest-bonanza-2014/2
Locking this thread 🙂