Because the license uses the framework of CopyRight to create a IntellectualProperty regime that puts work into a Commons rather than private hands, this style of license is commonly referred to as CopyLeft. That refers to both the incredible hack of CopyRight it represents, as well as its "left-wing" values.
The GNU General Public License can be found at the Free Software Foundation website. If you wish to read it here: http://www.fsf.org/licenses/gpl.html