title: Need advice on attribution/copyright of heavily modified OSS code (BSD, Apache, etc) in source headers
body: <p>I've got a question about use of permissive-licensed (BSD, Apache, MIT, etc) source where the line may be heavily blurred between original code and borrowed code. </p>
  
  <p>We are more than happy to disclose a copyrights for original source as required by the licenses.</p>
  
  <p>The specific case I'm wondering about is how to correctly update source headers in files I've modified. </p>
  
  <p>Assume you have some source from another project you'd like to make use of. It contains a header like the following.</p>
  
  <pre><code>/*
   * Copyright (C) 2006, 2007 John Doe.
   * Copyright (C) 2008, 2009 Project comitters.
   * All rights reserved.
   *
   * The software in this package is published under the terms of the BSD
   * style license a copy of which has been included with this distribution in
   * the LICENSE.txt file.
   * 
   * Created on 07. March 2004 by John Doe
   */
  </code></pre>
  
  <p>For a trivial bug fix, I would just make my small change, send it upstream and hope the fix gets incorporated. When it does, I would drop my patched version and go back to mainline.</p>
  
  <p>Some times I want to use the source as a jumping off point. It gets transformed over time and reworked and improved. It may resemble the original code but it certainly would be our own work by that point.</p>
  
  <p>Is it ok then to replace that header with my own? Should I just write something like "Based on original XYZ by John Doe"? </p>