How to (not) use GPL Software
The GNU GPL revisited

Revisiting the GNU General Public License

Regulates distribution of copyrighted code, not usage
Allows distribution of source code and modified source code
The license itself is mentioned
A copy of the license accompanies every copy
Allows distribution of binaries or modified binaries, if
The license itself is mentioned
A copy of the license accompanies every copy
The complete source code is either included with the copy (alternatively a written offer to send the source code on request to any 3rd party)