Public Boards can be viewed by every user in KanBo as well as added to his Personal KanBo Home. View access doesn't depend on having any permission to the Board. In the Public Boards, users can join a Board by their own decision and action (if the Joining Mode is enabled).
You can now disable possibility to create public boards in KanBo configuration.
Go to your KanBo's web.config and open it in any text editor.
In the <appsettings> section, change
<add key="KanBoAllowPublicBoards" value="true" />
<add key="KanBoAllowPublicBoards" value="false" />
Customer support service by UserEcho