[devel] Mention zlib-libpng license in each source file
diff --git a/scripts/makefile.os2 b/scripts/makefile.os2
index 1704acc..c250445 100644
--- a/scripts/makefile.os2
+++ b/scripts/makefile.os2
@@ -1,4 +1,6 @@
 # makefile for libpng on OS/2 with gcc
+#
+# This code is released under the zlib-libpng license.
 # For conditions of distribution and use, see copyright notice in png.h
 
 # Related files: pngos2.def