[Docs] Add licensing header to C data interface in docs

[stefan6419846]

Describe the enhancement requested

At https://arrow.apache.org/docs/format/CDataInterface.html#structure-definitions, a header file for the C data interface is provided. It does not carry any direct license headers, but states:

Like the rest of the Arrow project, they are available under the Apache License 2.0.

This can cause confusion for further redistribution and/or requires each user to correctly apply the corresponding header, while a recommended declaration could be provided by the Arrow project directly.

Depending on how you read/interpret the Apache-2.0 license in this regard, adding a license header myself could require me to add an explicit notice about me having added the license header (section 4b) and possibly even including the NOTICE.txt file of the Arrow project (section 4d).

Component(s)

Documentation

[omertt27]

Hi, I'd like to work on this issue @stefan6419846

[stefan6419846]

I am the reporter of this issue and no maintainer, thus it is not up to me to decide or assign anything here.

[kou]

Good point.

I think that we should add our license header and NOTICE content only for these definitions:

diff --git a/docs/source/format/CDataInterface.rst b/docs/source/format/CDataInterface.rst
index fd9952b037..cd51f98da7 100644
--- a/docs/source/format/CDataInterface.rst
+++ b/docs/source/format/CDataInterface.rst
@@ -277,6 +277,26 @@ are available under the Apache License 2.0.
 
 .. code-block:: c
 
+   // Licensed to the Apache Software Foundation (ASF) under one
+   // or more contributor license agreements.  See the NOTICE file
+   // distributed with this work for additional information
+   // regarding copyright ownership.  The ASF licenses this file
+   // to you 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.
+   //
+   // Apache Arrow
+   // Copyright 2020-2026 The Apache Software Foundation
+
    #ifndef ARROW_C_DATA_INTERFACE
    #define ARROW_C_DATA_INTERFACE
 

See also:

• https://www.apache.org/legal/src-headers.html#headers
• https://www.apache.org/legal/src-headers.html#notice

Could you start a discussion thread for this on our dev@arrow.apache.org mailing list for wider visibility?
https://arrow.apache.org/community/#mailing-lists