legal: selinux.c: Split Copyright notice & use same license as upstream

[kmk3]

selinux.c: Split Copyright notice in two

This makes firejail's Copyright notice match the ones in basically
every other file, which simplifies updating the Copyright years.

selinux.c was added on commit 1ad2d54 ("Add support for SELinux
labeling", 2020-02-18) and it claims to be "from systemd
selinux-util.c".

As for systemd's Copyright notice, the current version of that file on
the systemd project does not have any[1].

The first commit in the systemd repository is from 2009[2] and the file
was copied in 2020 (and does not seem to have been synced since), so set
the years in its Copyright notice to 2009-2020.

Since there is no Copyright notice (and no author) in the upstream file,
list "The systemd Authors" in the Copyright notice.

See also systemd commit 0c69794138 ("tree-wide: remove Lennart's
copyright lines", 2018-06-12)[3] [4].

[1] https://github.com/systemd/systemd/blob/254d1313ae5a69c08c9b93032aaaf3d6083cfc07/src/shared/selinux-util.c
[2] systemd/systemd@6091827
[3] systemd/systemd@0c69794
[4] systemd/systemd#9274

---

selinux.c: Use same license as upstream file (LGPLv2.1+)

The upstream file is licensed under the LGPLv2.1+ and it uses an SPDX
license identifier rather than an LGPL license notice[1].

And according to the GNU project, the LGPLv2.1+ is compatible with both
the GPLv2 (with the result being GPLv2) and the GPLv3 (with the result
being GPLv3), though the reverse (GPL -> LGPL) does not apply[2] [3].
This means that if we make changes that are only available under the
GPLv2, systemd would be unable to copy them back and release the result
under the LGPLv2.1 without being in violation of the GPLv2.

So replace the GPL license notice with the SPDX license identifier of
the upstream file ("LGPL-2.1-or-later"), to make it easier to share
changes between both projects.

See also the following systemd commits[4] [5] [6] [7]:

• 53e1b68390 ("Add SPDX license identifiers to source files under the
  LGPL", 2017-11-18)
• db9ecf0501 ("license: LGPL-2.1+ -> LGPL-2.1-or-later", 2020-11-09)

[1] https://github.com/systemd/systemd/blob/254d1313ae5a69c08c9b93032aaaf3d6083cfc07/src/shared/selinux-util.c
[2] https://www.gnu.org/licenses/license-list.en.html#LGPLv2.1
[3] https://www.gnu.org/licenses/license-compatibility.html
[4] systemd/systemd@53e1b68
[5] systemd/systemd#7386
[6] systemd/systemd@db9ecf0
[7] systemd/systemd#17548

---

This is a follow-up to #5664.

Cc: @reinerh @smitsohu @topimiettinen (as contributors to selinux.c)

[netblue30]

all in, thanks!

[topimiettinen]

It seems that it's not possible to approve the changes after they're committed, but I approve the license change (if anyone cares).

[topimiettinen]

(and sorry for being a bit slow these days)

[kmk3]

@topimiettinen on Feb 19:

It seems that it's not possible to approve the changes after they're
committed, but I approve the license change (if anyone cares).

Thanks for the review. I think it's important to get a yes/no for these things
for the avoidance of doubt, even if it's at a later date.

If anyone else wants to comment, feel free to do so.

(and sorry for being a bit slow these days)

All good; take care!

[reinerh]

It's also fine for me.