“In order to understand the GNU General Public License, first
you have to understand what free software means. Free Software
means software that respects the users’ freedom. Software that’s
not free is proprietary software. Non-free software, user
subjugating software, is distributed in a social system that keeps
the users the divided and helpless. Divided because every user is
forbidden to share the program with anyone else and helpless
because the users don’t have the source code, so they can’t change
it, they have no control over it, and they can’t even verify
independently what it’s really doing. It may have malicious
features, quite often it does, and the users may not even be able
to tell what malicious features it has…”