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Although I have found similar questions on this site they were not what I was looking for.

I have modified the source code of an MIT licensed project, and I have added new classes to it as well. Please correct me if I am wrong, but I think that it is legal to add my copyright notice above the license and remove the other one. But how should I attribute the contribution of the previous authors? Should I use a separate file? There are also some html files with no license or copyright notice in them which I also modified. Do I have to handle them differently?

My question is different than this question in that I have also modified some of the files of the project I am extending.

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The original license still applies to your modifications. I wouldn't appreciate somebody making modifications to something I published then decides to replace the copyright notice. The original notice still applies. The question's answer you linked applies to your question. –  Ramhound Dec 4 '12 at 12:25
    
So the answer is to keep the copyright notice but how do I indicate that the code was modified? Can I add my name-organisation next to the copyright? Of course I am going to keep the license in the modified code –  kon psych Dec 4 '12 at 12:43
    
Just add your own copyright notice? The original copyright and MIT license applies to your code, doesn't matter if you modify the existing code, the entire library ( present and future ) is licensed. –  Ramhound Dec 4 '12 at 12:49
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2 Answers

up vote 5 down vote accepted

I am not a lawyer, but according to the MIT license:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

Therefore you may not remove the existing copyright notice. You may only add your copyright notice and license terms to portions of code that you own the copyright to, which are your new or modified code.

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Your answer was helpful although it is not clear to me how I will add my copyright notice to modified code. I will probably include it in the Javadoc of my functions but I cannot and it does not worth to document every line I changed. –  kon psych Dec 4 '12 at 14:49
    
It's not clear to me either! Most people would not bother to document every line they changed. I suppose if it ever came down to a legal issue you would just diff the other project with your project. –  M. Dudley Dec 4 '12 at 17:08
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Please correct me if I am wrong, but I think that it is legal to add my copyright notice above the license and remove the other one.

You cannot delete the original copyright notice. That's out-and-out illegal.

Whether you can add your own notice is a bit dicey, and I am not a lawyer. What you have created falls into the category of "Derivative Works."

From US Copyright Office Circular 14: Derivative Works:

To be copyrightable, a derivative work must be different enough from the original to be regarded as a "new work" or must contain a substantial amount of new material. Making minor changes or additions of little substance to a preexisting work will not qualify the work as a new version for copyright purposes. The new material must be original and copyrightable in itself. Titles, short phrases, and format, for example, are not copyrightable.

If your changes do constitute copyrightable material, your copyright only pertains to your contributions. It does not pertain to the preexisting material.

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So if there is just one license.txt is it appropriate to add the names of the contributors under the original author in that one file –  user82793 Sep 17 '13 at 15:13
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