Post Terms As Class Name For Full Calendar Events

You are using get_single_term in a way that would require it to return a value…

$term = get_single_term($post->ID, 'course_locations');

… but you have written it in such a way that it echos a value. You should have…

function get_single_term($post_id, $taxonomy) {
  $terms = wp_get_object_terms($post_id, $taxonomy);
  if(!is_wp_error($terms))
  {
    return $terms[0]->name;   
  } 
}

I noticed a couple of other things not directly related to the question but worth mentioning.

1. You really should be using the AJAX API. includeing wp-load.php like that is a kind of hack, in my opinion, that is no longer necessary. It is also prone to error. Imagine if someone were to move one or more of the content directories.
2. You should really learn to indent your code. You are going to run into all kinds of headaches trying to debug “flat” code like that.