Input (grade 5): The source code to the Duke Nukem 3D v1 .5 executable, which uses the Build engine, was released as free and open source software under the GPL on April 1, 2003.
Output (grade 5): The source code to the Duke Nukem 3D v1 .5 executable, which uses the Build engine, was released as free software under the GPL on April 1, 2003.