Hi,

Dunno If I am right, but look into the code of spam.el revealed this to
me :

(defcustom spam-bogofilter-database-directory nil
  "Directory path of the Bogofilter databases."
  :type '(choice (directory 
                  :tag "Location of the Bogofilter database directory")
                 (const :tag "Use the default"))
  :group 'spam-ifile)
            ^^^^^^^^^^

Correct me if I am wrong but I think it would be better to have it in
the right customization group aka 'spam-bogofilter', no ?

If yes, then here is a small patch (my 1st contribution for Gnus :))

Cheers,

zeDek