You must be reading in my mind. Yesterday I coded a little dropdown_categories() template function, and I didn't test it yet. There I go, it works perfectly. There shall also be list_categories(), for those who don't want a dropdown menu.

About the license, there's still a copyright thing because b2 doesn't have a particular license upon it. Suffice to say that for the moment I don't really care if you use parts of my code or not, as long as you give me credits for it. And to clear things: opensource doesn't mean no-copyright, it just means that the end-user is allowed to view the source and change it as desired. b2 isn't released under the GPL yet.