 either let profiles persist (the ideal solution), or
  otherwise to alter the bluej.defs file supplied with BlueJ to include the
  line:</p>

<pre>blackbox.uuid=optout</pre>
</div>

<span class="question-heading" id="global_optout">I'm a network administrator; how I do
  disable participation for my users?</span>

<div class="answer">
<p>
  If you want to opt-out your users by default but still allow them to
  choose to opt-in later, you can alter the bluej.defs file that is
  install with BlueJ to include