The white label widget strictly requires jQuery to operate.
But jQuery can peacefully co-exist with other libraries on the same page via it’s $.noConflict() method. That makes using the widget on such pages as long as jQuery is included easy.
The only requirement is to call $.noConflict() immediately after the jQuery script tag:
... other libraries ...
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script>$.noConflict();</script>
<script src="http://whitelabeldemo.skyscanner.net/scripts/widget/sswidget.load.v1.min.js?&product=flights&newWindow=true"></script>