[Sandman]

Sure, you can reverse engineer a piece of software. But that's working around an obstacle. The point of free software is that there are no obstacles which would impair your ability to inspect, modify and change it in any way you see fit.

Also, I believe that most EULAs for non-free software have clauses which specifically forbid any attempt to reverse engineer it. I could be wrong, of course, but I doubt it.