Reuse is a specification that aims at making licensing of open source
software easier. You basically have to include an SPDX header in all
files, and when this isn't possible you create a file named
filename.license containing the header. While I find this a bit too much
this is also the only way of reliably determining the license and the
copyright holder of a certain file.

The use of SPDX tags has been adopted by projects like the Linux Kernel
(torvalds/linux/commit/a61127c2130236168321cc76c5a58e15c00ad154),
systemd, etc, and I find it way better that including a long copyright
notice on top of every file.

I didn't add any email address, but if you'd like to it is completely
possible to add them in the SPDX-FileCopyrightText tag, between angle
brackets.

The specification is available on https://reuse.software