Derrived work from BSD Licensed code

Question

I'm not exactly sure that stackoverflow is the right *overflow to post to concerning this, but w/e. Just don't flame me.

If i took a file with a BSD-style license (or MIT/X11, or ISC, or NCSA, etc.) and i modified/refactored/incorporated it into my own project, what is the procedure for distinguishing my vs. another copyright. I've refactored to such an extent that it wouldn't be practical to separate my own code from the original author's. If i wanted to add my own copyright to the code, do i just delete the original copyright notice and move it to an attribution file, then add my own notice? I understand that with these permissive licenses i am free to apply my own copyright/license to a derived work i create provided i retain the original copyright notice with the source/binary distribution. How would i fulfill these requirements? Since the original license comment at least gives the impression of having file scope, wouldn't it be confusing to have multiple copyright notices in a file?

In short, would it be sufficient to change the copyright notice to my own, and then provide a attrib/contrib file that says something along the lines of "this project incorporates code by X which is originally licensed under the terms of the following license: "? If not, what is the generally accepted method?

Answer 1

The terms of the BSD license dictate that you must retain the notice. If that is in source code, you cannot modify it. And conversely, if you distribute, make sure you show their copyright notice in your documentation. You can add your copyright in addition to theirs if you modify their source, but do not change or otherwise remove it.

Also keep in mind, that the BSD license does not allow sublicensing, which means, you cannot relicense their code under some other license for your purpose. However, it does not preclude you from including it in a work that is under a different, even more restrictive license.

Anyway, the easy thing for you to do is leave the comments which outline the BSD license and the copyright in the source files in tact, and produce them in documentation you ship with the binary (if you ship with the source, you need not perform that step, since you've left it in the source file).