Plugin error on install of Floating Social

Trying to install this plugin from the WPMU Dashboard and run into a problem. Up-to-date version of WordPress.

Plugin gives the following error on install:
The plugin generated 420 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.

Php errors on page refresh:

Strict Standards: Redefining already defined constructor for class Wdsb_AdminPages in [blah...]/public_html/wp-content/plugins/sharebox/lib/class_wdsb_admin_pages.php on line 11

Strict Standards: Non-static method Wdsb_AdminPages::serve() should not be called statically in [blah...]/public_html/wp-content/plugins/sharebox/sharebox.php on line 75