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Licence requirements when extending log4j

 
Sheriff
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We are using Log4j in our product and I needed to create a new Appender for a feature we are introducing. I'm wondering about the licensing implications for using this in production. Log4j uses the Apache 2.0 licence.

- The log4j package is untouched.
- I have taken a copy of an existing Log4j Appender class and placed it in our own package.
- I have lightly modified that copy to suit our requirements.
- I am using the modified copy in the log4j.xml configuration

I know very little about licensing issues so have no idea if I'm in breach or not, and if not do I need to attribute anything to the original author in my new Appender class?
 
Sheriff
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I have often used this site http://choosealicense.com/licenses/ to understand what each license allows or restricts. For Apache 2.0 license you can see it here http://choosealicense.com/licenses/apache-2.0/ (see the right side of that page which I found useful to understand how changes are expected to be attributed).
 
Tim Cooke
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That's a useful link, thanks Jaikiran. I think I understand that I'd need to put a licence notice on the file, and state that I had made changes, if I had made changes to the log4j library.

However, I have written my own Appender which extends AppenderSkeleton (log4j class) and have it packaged in my own application. Given that I have not made any modifications to the log4j package, I'm thinking that I don't need any licence or attribution in my extension class.

The only uncertainty I have is that my new Appender class is a copy of a log4j Appender with some minor modifications. It's the fact that a good part of the class is a straight copy, makes me wonder if attribution is required.
 
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