License for header exposing functions in a BSD 3 clause licensed source

Question

If I were to write a header exposing functions in a sample source file that was licensed under the BSD 3-Clause License, what would I put up in the header?

1. Should I simply copy-paste the license text in the implementation source file?
2. Should I add a line saying I modified it or added the header?

EDIT 1:

I realised my question wasn't very clear. Here's what the source .c file (written by some other person) looks like:

/*
 * Copyright (c) 2013 xxxx <[email protected]>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of mosquitto nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

int func1() {
    /* implementation */
    return 0;    
}

int func2() {
    /* implementation */
    return 0;    
}

And to use this file in my project, I wrote a .h that looks like this:

#ifndef SOURCE_H
#define SOURCE_H

int func1();

int func2();

#endif /* SOURCE_H */

Do I need to copy-paste the copyright notice from the .c file to the .h or is it sufficient to add the license text to my project license file?

Answer 1

The normal practice is that all files written as part of one project are all provided under the same copyright license. This means that you should at least copy over the license text that is used in the other (source) files in the project.

Whether you should add your name to the copyright statement can't really be answered by us. It depends mostly on how contributors to the project are normally recognized.

---

With the BSD license, which is used here, it is recommended that you indeed reproduce the entire license text in your files. That way, it is clear what license applies to the file, even if it gets separated from the rest of the project.

Some of the longer licenses (like GPL and Apache) have a comment block that refers the reader to the actual license text in a different file, but those blocks are not that much shorter than the full text of the BSD license.