title: Is there any open source implementation of APL?
body: <p>I am aware of J &amp; K; but neither are open source.</p>
  
  <p>I'm also aware of A+, but that seems outdated.</p>
  
  <p>Is there any decent open source implementation of APL?</p>
  
  <p>If so, where? If not, why?</p>