Multiple instances need to be applied to different elements in the DOM
otherwise multiple menus will be called for each click/right click.

e.g.

jQuery(document).ContextMenu(url);

would work for any form on a page. Using this would mean that multiple
instances couldn't be used though

jQuery('#content form').eq(0).ContextMenu(url);
jQuery('#content form').eq(3).ContextMenu(url);

Using the above 2 menus will be created for the first and 4th forms on
the page. Any of forms won't response to menu clicks.

jQuery(docuemnt).ContextMenu(url);
jQuery('#content form').eq(0).ContextMenu(url);

With the above any form on the page will respond to menu clicks but the
first form will send 2 requests for the context menu.