Original: The Blender Foundation initially reserved the right to use dual licensing, so that, in addition to GNU GPL, Blender would have been available also under the "Blender License", which did not require disclosing source code but required payments to the Blender Foundation.
Simplified: The Blender Foundation have the right to use dual licensing, so that, in addition to GNU GPL, Blender would also have the permission to use the following name: "Blender License".