I'm porting the ESRI geometry-api-java library to C#. They have placed the library under the Apache License. They also mention it in the README.md.

They have a small bit of licensing info in the header of each source file. Do I have to replace that header with my own Apache 2.0 License disclaimer? Or do I just leave theirs in place? Or do I append my own disclaimer below theirs?

Basically, I want to make this ported version of the library publicly available, but I don't want to get screwed by some lawyer.

  • How much are you changing during your “porting” efforts? If it essentially amounts to a re-write in another language where you only try to model the original API, then it is your own work.
    – 5gon12eder
    Commented Oct 15, 2015 at 10:49
  • @5gon12eder, I'm using the Sharpen tool in order to do an initial port. At that point it has thousands of errors. Then I have a about 500 lines of python script that takes it the rest of the way there (missing a few classes). It is almost completely the same library as the original.
    – David
    Commented Oct 15, 2015 at 10:53
  • 1
    Okay, if you use a tool to do a more or less “mechanical” transformation, then it is a derivative work still covered by the copyright of the original work.
    – 5gon12eder
    Commented Oct 15, 2015 at 10:54

1 Answer 1


The answer can be found right in the license text (emphasis mine).

  1. Redistribution. You may reproduce and distribute copies of the Work or Derivative Works thereof in any medium, with or without modifications, and in Source or Object form, provided that You meet the following conditions:

    (a) You must give any other recipients of the Work or Derivative Works a copy of this License; and

    (b) You must cause any modified files to carry prominent notices stating that You changed the files; and

    (c) You must retain, in the Source form of any Derivative Works that You distribute, all copyright, patent, trademark, and attribution notices from the Source form of the Work, excluding those notices that do not pertain to any part of the Derivative Works; and

    (d) If the Work includes a "NOTICE" text file as part of its distribution, then any Derivative Works that You distribute must include a readable copy of the attribution notices contained within such NOTICE file, excluding those notices that do not pertain to any part of the Derivative Works, in at least one of the following places: within a NOTICE text file distributed as part of the Derivative Works; within the Source form or documentation, if provided along with the Derivative Works; or, within a display generated by the Derivative Works, if and wherever such third-party notices normally appear. The contents of the NOTICE file are for informational purposes only and do not modify the License. You may add Your own attribution notices within Derivative Works that You distribute, alongside or as an addendum to the NOTICE text from the Work, provided that such additional attribution notices cannot be construed as modifying the License.

    You may add Your own copyright statement to Your modifications and may provide additional or different license terms and conditions for use, reproduction, or distribution of Your modifications, or for any such Derivative Works as a whole, provided Your use, reproduction, and distribution of the Work otherwise complies with the conditions stated in this License.

So, in short, yes, you must keep their original copyright notice and add a notice that you edited the file. In addition, you may add your own copyright notice if you want. (I recommend you do.)

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