It looks like there is another project geared towards Views Highcharts integration at http://drupal.org/sandbox/fadeddata/1117398. Although that one is for D6 Views 2 and yours is for D7 Views 3, it might be worth seeing if there is any potential for collaboration. It this sandbox gets promoted to a full project, maybe the maintainers of the other project can be integrated in to work on the D6 version.