The FSF holds the copyrights on many important pieces of the GNU system, such as the GCC. As a copyright holder, it has the power to enforce the GNU General Public License (GPL) when copyright infringement occurs on that software. While other copyright holders of other software systems used the GPL as their license, FSF was the only organization to regularly assert its copyright interests on software licensed under the GPL until Harald Welte created gpl-violations.org in 2004.