diff --git a/content/_code-samples/key-derivation/RFC1751.py b/content/_code-samples/key-derivation/RFC1751.py
index 789289560b..51acc15aa3 100644
--- a/content/_code-samples/key-derivation/RFC1751.py
+++ b/content/_code-samples/key-derivation/RFC1751.py
@@ -2,6 +2,7 @@
 # https://github.com/dlitz/pycrypto/blob/master/lib/Crypto/Util/RFC1751.py
 # This version has been adapted to Python 3 using the '2to3' utility
 # and manually adjusted for better Python 3 compatibility.
+# Those revisions are released to the public domain.
 
 # rfc1751.py : Converts between 128-bit strings and a human-readable
 # sequence of words, as defined in RFC1751: "A Convention for
diff --git a/content/_code-samples/key-derivation/ed25519.py b/content/_code-samples/key-derivation/ed25519.py
index 077f25269f..adda08c1e2 100644
--- a/content/_code-samples/key-derivation/ed25519.py
+++ b/content/_code-samples/key-derivation/ed25519.py
@@ -1,5 +1,6 @@
 # Python Implementation from https://ed25519.cr.yp.to/software.html
-# Adjusted to Python 3 syntax by rome@ripple.com
+# Adjusted to Python 3 syntax by rome@ripple.com. The revisions are
+# released to the public domain.
 # Public domain software. This is a reference implementation that
 # does not include recommended speed & security optimizations.
 
diff --git a/content/_code-samples/key-derivation/key-derivation.py b/content/_code-samples/key-derivation/key-derivation.py
index b2f7c8f879..9116565001 100755
--- a/content/_code-samples/key-derivation/key-derivation.py
+++ b/content/_code-samples/key-derivation/key-derivation.py
@@ -1,8 +1,18 @@
 #!/usr/bin/env python3
 
+################################################################################
 # XRPL Key Derivation Code
 # Author: rome@ripple.com
 # Copyright Ripple 2019
+# This sample code is provided as a reference for educational purposes. It is
+# not optimized for speed or for security. Use this code at your own risk and
+# exercise due caution before using it with real money or infrastructure.
+# This file is provided under the MIT license along with the rest of the
+# XRP Ledger Dev Portal docs and sample code:
+# https://github.com/ripple/xrpl-dev-portal/blob/master/LICENSE
+# Some of its dependencies are released under other licenses or are adapted
+# from public domain code. See their respective files for details.
+################################################################################
 
 import argparse
 import sys