BBJ is heavily inspired by image boards like 4chan, but it offers a simple account system to allow users to identify themselves and set profile attributes like a more traditional forum. Registration is optional and there are only minimal restrictions on anonymous participation.
Being a command-line-oriented text board, BBJ has no avatars or file sharing capabilties, so its easier to administrate and can't be used to distribute illegal content like imageboards. It has very few dependancies and is easy to set up.
The API is simple and doesn't use require complex authorization schemes or session management.