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Case is following:

Someone has released software under ISC license, and the source code file has following section at the beginning

Copyright (c) 2015, 2018 John Doe

Permission to use, copy, modify, and distribute this software for any...

If some other party modifies some parts of this software and then releases it under ISC license, how should the copyright part be written? Should both names be mentioned?

The source code might not go to version control system, so it won't be trivial to figure out who wrote what parts.

marked as duplicate by amon, Mureinik, Mick, Bart van Ingen Schenau, Community Nov 14 '18 at 18:08

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