How to add Contribution By column
I'd wager that the template you're looking at calls hook_civicrm_searchColumns.  Despite the name referring to "search", it's designed to let you change the values of the columns in tables like the one you display.

I just pushed a simple extension that demonstrates how it's used: https://github.com/PalanteJon/org.takethestreets.campaignincontributiontab/blob/master/campaignincontributiontab.php