Good question
In the code it is adding the link <a href....> for each category and sub-category... basically you just need to have an IF category is top-level category (no a href link) ELSE if not then include the <a href link...
This could also be done with CSS I guess (using a different style tag if is top category).
If you are not sure how to do this (change the code) and have bought someones third party module - then ask them to help... as I think they could code this for you in a couple of minutes (and might even be nice enough to not charge more than a couple of dollars).
Cheers - Asiaplay
PS: I am not a programmer - just trying to help with a solution for you which is built into the existing cart or can be easily done (hence why not given you the code change for this).