Didn't work for me at all…

I used it in a WordPress 4.2.2 and it removed the Private words but added the numbers back on after the Forum name. I still could not see the Forum names when I logged out and once you install and activate it, it will not add the plugin to your active plugins, so if it doesn’t work you will have to manually delete it. also using bbPress 2.5.8

https://wordpress.org/plugins/bbp-private-forum-visibility/