Part 1 of adding REUSE-lintable copyright and license info to files

[jafingerhut]

No description provided.

[jafingerhut]

See this comment on a recent similar p4-spec repository PR that explains the rationale for REUSE, and some of its mechanics: p4lang/p4-spec#1395 (comment)

[jafingerhut]

This is ready for review. I realize it is not of a size convenient for review, so here is how these changes were created, if you trust me. I was pretty careful.

Every file in third_party I went through and checked who the copyright holder was, and what license was in the file, if any. I kept those licenses as they were. They were all things compatible with Apache-2.0, such as MIT, BSD-2-Clause, BSD-3-Clause, and one custom license that was similar to BSD-2-Clause, but not the same, so I created a custom license file for it in LICENSES/ directory.

For all files that already had an Apache-2.0 license explicitly mentioned in the file, I was sure to keep those files as Apache-2.0. This was most of the C/C++ source files in the repo. I maintained their copyright holders.

The same goes for the remaining few C/C++ source files that did not have an explicit Apache-2.0 license. I used the Apache-2.0 license for them. There were only a few of them, and they did not mention any other license explicitly in their comments, and they were typically added in the same commits as other files with an Apache-2.0 license, and/or by authors working for Barefoot Networks at the time of adding the file.

For infrastructure files, e.g. yml, sh, CMakeLists.txt etc. I used Apache-2.0, and maintained the copyright holder and year in the file if there was one, otherwise I used the year the file was first added to the repo as the copyright year, and the name of the first commit Author as the copyright holder, unless I knew they were working for Barefoot Networks at the time, in which case I used Barefoot Networks.

No proprietary/confidential files were found.

There are a handful of files with suffix .m4 for Automake that are GPL, but they have an explicit exception in their licnese that allows the output generated from them to be used for non-GPL'd projects.