Latest compatible version of Classicube from the original GitHub repository (https://github.com/ClassiCube/ClassiCube) that can be compiled on Classicube for PowerMac PPC running Mac OS X 10.4.

misc/wiiu/ps_textured_lin.glsl

@@ -0,0 +1,14 @@
+varying vec4 out_col;
+varying vec2 out_uv;
+
+uniform sampler2D texImage;
+uniform vec3 fogCol;
+uniform float fogEnd;
+
+void main() {
+  vec4 col = texture(texImage, out_uv) * out_col;
+  float depth = 1.0 / gl_FragCoord.w;
+  float f = clamp(1.0 - fogEnd * depth, 0.0, 1.0);
+  col.rgb = mix(fogCol, col.rgb, f);
+  gl_FragColor = col;
+}