Microsoft Windows is a clear and instructive example of nonfree software. Its source code is a secret, so programmers cannot learn from it, fix it, adapt it to their clients (your) needs, or even verify what it really does. If you share copies with your neighbors, you will be called a “pirate”, and users have been threatened with imprisonment for this. Nonfree software is completely controlled by its developer, who also has power over the users. We started the free software movement because this power is unjust .