Should I include a copyright line in every file?

Question

This is similar to my other question, but specifically about Copyright rather than Licensing.

Typically, each source file contains a line of the form

Copyright 2010-2015, Me

• Is this strictly necessary, or would a single COPYRIGHT file at the root of the repository cover all files within the project?
• Do I need a separate COPYRIGHT file as well, to cover the entire project as a collection, rather than individual files?
• If I have a copyright line in each source file, should they all reflect the same year range? Or should each file's line reflect the year-range from creation to the year it was last modified?

Answer 1

I think it's important to include both copyright and licensing information in all files: it ensures that everyone's rights are perfectly clear, regardless of what happens to the code in the future. Your project may be small and self-contained initially, but it often happens that interesting code ends up copied into multiple projects, or that projects get adopted by various people down the line. In both cases it's much easier to keep track of licenses and copyright information if it's specified in every file.

If you consider large projects nowadays, many of them include code from a huge variety of other projects, some large, some small, and in some cases single files copied from various sources (including sometimes old Usenet posts!). Firefox is a good example of this; it includes files from many different projects, some quite small (included in Firefox here), and it can be quite hard to keep track of all the copyright holders and license information. Having it in every single file makes license auditors' jobs much easier.

There have been cases in the past of projects which couldn't be included in Linux distributions because of a couple of files whose licenses or copyright information wasn't clear... (I don't remember specifics off the top of my head, I could find them if necessary.)

Luis Villa wrote an interesting blog post on the topic.

As far as the difference between copyright and licensing goes, they are different, but licensing depends on copyright: a license is only valid inasmuch as it was originally given by the copyright holder. This reinforces the importance of including copyright information: it allows future users of your code to know who wrote it, and who to contact with any copyright-related queries (including licensing questions).

Concerning copyright years, I'll defer to the GPL howto (I don't know the reasoning behind this rule but it's probably applicable beyond just the GPL): according to the FSF, copyright statements are supposed to list the years in which the project was released, not the years in which modifications occurred. So any file which is part of a release should have its copyright statement updated on release; there are a number of tools which can automate this (copyright-update-directory in Emacs to name one). You can end up with different year ranges in your source files, but based on the first release they were part of.

Answer 2

I'm just going to add to Trevor's answer.

If the license that you're using says something by this, then by all means you should follow it. Otherwise, I think a single file that explains that the copyright applies to all files in the repository should suffice.

Answer 3

This is partially based on preference.

If you are distributing / publishing something as a package with one license included there is no need to put the licence on every page. However if you are making a website you may want to reference the license / put the copyright notice on every page to make people aware of the licence your work is published under.