diff --git a/netopeer/voltha-transapi/voltha.yang b/netopeer/voltha-transapi/voltha.yang
index 3b15ebf..78642da 100644
--- a/netopeer/voltha-transapi/voltha.yang
+++ b/netopeer/voltha-transapi/voltha.yang
@@ -1,3 +1,18 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+
+ * 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.
+ */
 
 module voltha {