You just translate these lines and overwrite them like that:
$doWeek = false; // false - current month and true - current week
$maxusers = 5; // max users to display
$adminName = "youradmin"; // if you want to ignore the admin, define his name
$localcode = "en_US";
$langActUsers = "Most Active Users"; // your language string
$langThisWeek = "this week"; // your language string for 'this week'
PS: I know it would be better to have a separate language file, but when releasing the plugin I did not know how to do it. So maybe a will update it next month.