For some reason it's not possible to go to theme settings page (for example /admin/appearance/settings/bartik) if fb module is enabled:

Fatal error: Cannot redeclare fb_admin_page() (previously declared in /sites/all/modules/fb/fb.admin.inc:21) in /sites/all/modules/fb/fb.admin.inc on line 108

It seems to me the module requires itself several times. So, it's better to use include_once instead of include in /sites/all/modules/fb/fb_app.admin.inc