title: GPL: you know how it's done, but you have'nt seen the code, is then your own code GPL?
body: <p>Please imagine such a sutuation:</p>
  
  <ol>
  <li>You found a piese of GPL'ed software. The software does thing "A".</li>
  <li>Without looking at the source code of "A", you implement the same functionality of "A" yourself and put it into "MyA.cpp".</li>
  <li>In such a case, do you have to license "MyA.cpp" as GPL?</li>
  </ol>
  
  <p>Thanks in advance for your answer.</p>