GNU GPL

See the following -

'Open Source' Is Not 'Free Software'

In the open source universe, using terms such as FLOSS (Free/Libre and Open Source Software) is common and represents a casual conflation of the terms open source and free software, which are often used interchangeably. I would be remiss if I didn't also admit that I have been guilty of same. I won't be doing that anymore—or at least I'll try not to—for a simple reason: Using the terms interchangeably is dangerous to the goals of free software and open media advocates (read "anti-DRM"). To continue this practice is to undermine beliefs that are fundamental to free software and associated movement...