Print the node author's full name on a custom node template
Your question doesn't indicate whether you are storing the user's full name anywhere. You can add fields to the user profile (at /admin/config/people/accounts/fields). Suppose you add a firstname field (field_user_fname) and lastname field (field_user_lname), you could then write a custom function in your template file, like this:

function _get_author_name($uid) {
  $wrapper = entity_metadata_wrapper('user', $uid);
  $fname = $wrapper-&gt;field_user_fname-&gt;value();
  $lname = $wrapper-&gt;field_user_lname-&gt;value();
  return "$fname $lname";
}


And then, since you already know the UID, you could call the function from your content template:

&lt;div class="author-name"&gt;
    WRITTEN BY &lt;a href="/user-posts/&lt;?php print $uid; ?&gt;"&gt; 
    &lt;?php print _get_author_name($uid); ?&gt;&lt;/a&gt;
  &lt;/div&gt;


You could also investigate the Realname module.