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>

projects/schfs-linux/README.md

@@ -61,12 +61,8 @@ how you end up maintaining two of them.
 
 ## Licence
 
-Apache-2.0. See [LICENSE](LICENSE).
+GPL-2.0-or-later, like the rest of SchOS. See [LICENSE](LICENSE).
 
-Apache-2.0 rather than MIT or BSD for one reason that matters at this level: it
-contains an express patent grant and a patent-retaliation clause. MIT and BSD
-are silent on patents, which means a contributor can hand you code and later
-assert a patent over it.
-
-Note that a Linux **kernel module** is a different licensing question from FUSE,
-and one reason the FUSE implementation comes first.
+That also settles the kernel-module question in advance: a Linux module under a
+GPL-compatible licence can use `EXPORT_SYMBOL_GPL` interfaces and does not taint
+the kernel. The FUSE implementation still comes first, for the reason above.