Giving proper credit to a projects contributors

Question

I've recently been working with an opensource library for a commercial product. The opensource code is distributed from the website of the company who sells the proprietary product as a zip file.

The library is a (direct) port to C# of the original library which is in Java. As such, it uses methods instead of getter/setter properties. The code contains copyright notices to the supplier of the product. The C# port was originally provided to the company by a 3rd party individual.

I have modified the source to be more C# like and added a couple of small features.

I want to put my version of the code out there (Google code or where ever) so that C# users of the software can benefit from a more native feeling library.

How can I and/or how should I amend the copyright notice to give proper credit to

1. The comercial owner of the original source
2. The guy who provided the original C# port
3. Myself and anyone else who contributes to the project in the future

The source is provided under the LGPL V2.1,

Answer 1

Usually it is best to get copyright assignment from all contributors to an Open Source project to give you the ability to change licensing terms in case of problems in the future. The Free Software Foundation and Apache handle copyright this way. This enables you to put Copyright (C) 2010 <YOUR PROJECT> in the code files and keep a CONTRIBUTORS file with the names of everybody who contributed.

In your case though there is existing copyright on the files which you cannot remove. The typical way would now be to put the names and years of the contributors underneath each other at the top of each file:

Copyright (C) <year> <name of commercial owner>
Copyright (C) <year> <name of guy who ported the code>
Copyright (C) <year> <name of your Open Source project if using copyright assignment or individual names>

Apart from this I would keep a contributors files listing all notable contributors for a better overview.