Call Cost Module

Hello

I have had no luck in getting the cdrcost module to work. It installs and creates the various tables in the Asterisk database and the cdrcost table in the cdrdb.
However the cdrcost table never gets any data written to it, even after setting a cron job to periodically do this.

/var/log/httpd/error_log shows a lot of entries like the following:

Undefined variable: action in /var/www/html/admin/modules/cdrcost/functions.inc.php on line 50
Undefined variable: action in /var/www/html/admin/modules/cdrcost/functions.inc.php on line 54
Undefined variable: action in /var/www/html/admin/modules/cdrcost/functions.inc.php on line 58
Undefined variable: action in /var/www/html/admin/modules/cdrcost/functions.inc.php on line 29
Undefined variable: extdisplay in /var/www/html/admin/modules/cdrcost/functions.inc.php on line 33
…etc etc

I am trying to use this module with trixbox 2.6.2.1, and would like to know if it is just plain broken or is this an incompatibility issue with trixbox.
I know the module is unsupported but it looks like quite a lot of work has gone into it. For me it would be a really useful alternative to A2billing-type solutions which are overly complicated for my small application.
Any advice would be appreciated.