diff --git a/src/swrenderer/things/r_voxel.cpp b/src/swrenderer/things/r_voxel.cpp
index aeca11b21..597aa7a84 100644
--- a/src/swrenderer/things/r_voxel.cpp
+++ b/src/swrenderer/things/r_voxel.cpp
@@ -6,21 +6,13 @@
 // Copyright(c) 1998 - 2016 Randy Heit
 // All rights reserved.
 //
-// This program is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
+// Draw a voxel slab. This function is taken from the Build Engine.
 //
-// This program is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with this program.  If not, see http://www.gnu.org/licenses/
-//
-//--------------------------------------------------------------------------
+// "Build Engine & Tools" Copyright (c) 1993-1997 Ken Silverman
+// Ken Silverman's official web site: "http://www.advsys.net/ken"
 //
+// Permission has been obtained to use this code under the terms of
+// the GNU General Public License v3.0.
 
 #include <stdlib.h>
 #include "templates.h"