Good News - MS Windows Source Code Leaked

Ed Felten on his Freedom to Tinker blog breaks some incredibly good news - Windows 2000 and Windows NT4 source code has been leaked on the internet (Windows Source Code Leaked?). Microsoft has apparently confirmed the leak, according to the AP wirestory on SecurityFocus.com (Microsoft source code leaked over Internet) Though Felten is rightfully worried that malware authors will have a field day, there are a number of positive developments that can occur because of this (in no particular order):

• Search MS source code for evidence of theft from open source projects;
  
• Search MS source code for evidence of antitrust violations ("Windows isn't finished until * won't run");
  
• Reverse engineer MS souce code for greater compatibility with all sorts of open source projects;
  
• Reverse engineer MS source code for Windows emulators on Linux such as WINE or Lindows (note a comment by Seth Schoen here);
  
• Prove that the browser/media player/etc. can be removed from the operating system with little harm done;
  
• Reverse engineer MS source code to crack DRM schemes;
  
• Play with source code just because Bill Gates won't like it;
  

This is just a partial list, I am sure, of positive uses for the source code. Readers are kindly requested to submit more ideas.

There is also an interesting copyright question here. If I have a "license" for the executable version of MS Windows, is it a copyright violation for me to keep a backup copy of the source code? Am I violating copyright if I play with the source code at all?