I've been looking for various licenses that I can use for an open-source project of mine, but all of the projects that I've seen, with all kinds of licenses, appear to have a giant, obnoxious (in my opinion) notice in each source file that states that the file is listed under a certain license. I don't think that I've found a single source project that isn't public domain that doesn't have a notice like that.
This just seems like a waste of time and file space. I plan on putting @license and @author tags in my projects, but I don't see why I need to list such a giant notice in each individual file if I don't want to make my code public domain.
Is there any reason why I would want to include such a notice in my projects, or would simply including a notice in the README and a @license tag be good enough? Does this affect the "clearly stated" rule of most licenses, or is it just overkill so that people won't argue?
Best Answer
I've seen many projects which only mention the license in the README or in a LICENSE or COPYING file.
Your software is automatically covered under copyright, as agreed in international law. (Unless you are working for the US government or some other organization for which copyright does not apply.)
If someone uses your software then they must make sure to follow the license agreement, or follow the fair use restrictions on what they can do.
Suppose that person wants to use one of the files in your code distribution, which of course requires a copy and hence copyright law applies. By default they do NOT have the right to use your software under copyright law. It's only when they know and follow the license restrictions that they are allowed to use it.
So if they use a file without a software license then they are breaking copyright law. Since all the licenses say something like "The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software", they are obliged to put that license somewhere.
That can be in the file itself, or when I've used code as library I put the relevant portions into its own directory and added a "README" or "LICENSE" into that subdirectory.
In short, you don't need to put the license in each file. I think it's overkill. There's no extra legal protection in doing so. It does help a downstream user somewhat, but not by much.
I think the tradition of lots of comment-based metadata (license, creation date of each function, changelog, etc.) are very old traditions which exist because they are easy to do and which more a talisman than useful.
For example, the default Eclipse template adds what I think of as useless metadata before each function, which I think is much better captured by version control. But that practice is common in many shops.