Split function “the_tags” in 2 columns

Use get_the_tags instead of the_tags to grab an array of tags, and array_chunk to split it. You will then need to build a loop to display the tags.

$tags = get_the_tags(); 
if (!empty($tags)) {
  $tags = array_chunk($tags,ceil(count($tags)/2),true);
  foreach($tags as $v) {
    echo '<ul>';
    foreach ($v as $tag) {
      echo '<li><a href="'.get_tag_link($tag->term_id).'">' . $tag->name . '</a></li>'; 
    }
    echo '</ul>';
  }
}

Reference

http://codex.wordpress.org/Function_Reference/get_tag_link