Bugfix in K2 Multi-category extension

My website is running on Joomla 1.7.3 and the most recent version of K2. I purchased an extension that is supposed enable me assign multiple categories to K2 content, but it could not even install properly, talk less of working as promised and the vendor has gone AWOL I need someone who is familiar with Joomla 1.7x and K2 to make this extension work. The component is attached. You will be required to fix and demo it in an identical environment.