licence: SchOS is GPL-2.0-or-later, no longer Apache-2.0

Nexoniarz is the sole author and SchOS was never published under
Apache-2.0, so this is a straight relicence. LICENSE is the FSF GPLv2 text,
every first-party SPDX header moves to GPL-2.0-or-later, and NOTICE,
README.md, docs/licensing.md and the site say so. projects/schfs-linux
follows the rest of the tree.

The GPL gives copyleft: a fork has to ship its source. It also lifts the
old "Linux drivers, never" rule, since GPL-2.0-only code combines with
GPL-2.0-or-later. "Or later" leaves room for GPLv3, but one binary still
has to pick one version, so docs/licensing.md now keeps Apache-2.0 and
GPLv3 code out of the kernel to keep Linux code possible there. BSD
4-clause code goes from "avoid" to "no", because the advertising clause
is GPL-incompatible.

LDLS still ships no .ko. That boundary is now project policy rather than
a legal requirement, and ldls.md, devices.md and licensing.md section 6
say so. refmod declares license=GPL, and ldls-check passes (27 checks).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/plan/wayland.md

@@ -135,10 +135,9 @@ in `NOTICE` **before** the file is committed, not after.
 | libxkbcommon | MIT |
 | xkeyboard-config | MIT |
 
-All Apache-2.0 compatible, all needing only a `NOTICE` entry. **Nothing here
-carries the GPL problem that governs drivers**, which is a pleasant change and
-worth noticing: the Wayland ecosystem is permissively licensed almost throughout,
-and that is a genuine argument for it beyond any technical one.
+All GPL-2.0-or-later compatible, all needing only a `NOTICE` entry. The
+Wayland ecosystem is permissively licensed almost throughout, so nothing here
+raises a licensing question at all.
 
 ---