The GtkRadiant sources as originally released under the GPL license.

setup/data/tools/gl/zfill_vp.glsl

@@ -0,0 +1,35 @@
+/// ============================================================================
+/*
+Copyright (C) 2004 Robert Beckebans <trebor_7@users.sourceforge.net>
+Please see the file "CONTRIBUTORS" for a list of contributors
+
+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 2
+of the License, or (at your option) any later version.
+
+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, write to the Free Software
+Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+*/
+/// ============================================================================
+
+attribute vec4		attr_TexCoord0;
+
+void	main()
+{
+	// transform vertex position into homogenous clip-space
+	gl_Position = ftransform();
+	
+	// transform texcoords
+	gl_TexCoord[0] = gl_TextureMatrix[0] * gl_MultiTexCoord0;
+	
+	// assign color
+	gl_FrontColor = gl_Color;
+}