diff --git a/src/_zkapauthorizer/foolscap.py b/src/_zkapauthorizer/foolscap.py
index 67b1b2f7c0b2d55c76f8a37cf7d4e6b8cf499be6..7215dbc8d111ba0247e2fb47e853a1c6a2ee97fb 100644
--- a/src/_zkapauthorizer/foolscap.py
+++ b/src/_zkapauthorizer/foolscap.py
@@ -1,3 +1,22 @@
+# Copyright 2019 PrivateStorage.io, LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Definitions related to the Foolscap-based protocol used by ZKAPAuthorizer
+to communicate between storage clients and servers.
+"""
+
 from __future__ import (
     absolute_import,
 )