Syntex: This is exactly how it is designed to operate. You are supposed to add both those lines. But as Brian described, you haven't followed the integration instructions.
This line adds only the code that makes the mouse-over popup work
<?php $OL=1; require("calendar/calendar.php"); ?>
Then you need to add this line to make the calendar appear...
<?php require("calendar/calendar.php"); ?>
With only the first, you won't see anything on the front end... It only adds stuff in the code. With only the second one, the mouse-over won't work... So, no, nothing is wrong with your installation. But do fix where you added your first line like Brian said.
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