Call to undefined function: drupal_get_path() in ...jquery_cookie.module on line 106

I installed jquery_cookie, 5.x.1.x-dev 2007-10-14, to get a couple doodads (fontsizer). It works for me but some of the users are seeing blank screens and the following message appears in the error log:

[client xx.xx.xx.xx] PHP Fatal error:  Call to undefined function:  drupal_get_path() in /var/www/vhosts/visforvoltage.org/httpdocs/modules/jquery_cookie/jquery_cookie.module on line 106

This is the relavent code:

line 106 -->  //$module_dir = drupal_get_path('module', 'jquery_cookie');
  $module_dir = "modules/jquery_cookie";

You can see I commented out the line and substituted a hardcoded value. However that introduced another problem:-

[client xx.xx.xx.xx] PHP Fatal error:  Call to undefined function:  drupal_add_js() in /var/www/vhosts/visforvoltage.org/httpdocs/modules/jquery_cookie/jquery_cookie.module on line 109

The core problem is not all the functions are available when the init hook is available ???