I just downloaded Dashboard Builder, copied the files in a subdirectory of my Nginx web server (html/dashboardbuilder) with write access (running on Windwos 7).
When I want to run the installation, I use Firefox: localhost/dashboardbuilder/index.php
The address bar then displays localhost/dashboardbuilder/lib/ and the page displays a 403 Forbidden error.
I rechecked the dashboardbuilder and the lib directory access rights, both have read/write access.
I have other subdirectories of the html directory with other web applications, the PHP apps function without a hitch, so the bug seems to be specific to dashboardbuilder.