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>

kernel/fs/devfs.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 //
 // devtmpfs: /dev, generated rather than stored.
 //

kernel/fs/schfs/attr.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 //
 // Attributes, and the index over them.
 //

kernel/fs/schfs/btree.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 //
 // SchFS copy-on-write B-tree — see btree.h for the contract.
 //

kernel/fs/schfs/kmount.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 //
 // SchFS in the kernel: block device, mount, and the transaction bracket.
 //

kernel/fs/schfs/obj.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 //
 // SchFS object layer, read side: inodes, directories and file data.
 //

kernel/fs/schfs/objw.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 //
 // SchFS object layer, write side: create, link, unlink, rename, write,
 // truncate.

kernel/fs/schfs/schfs_int.h

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 //
 // SchFS internals: the volume (uberblock ring, block allocation) and the object
 // layer (inodes, directories, file data) that sit on top of the B-tree.

kernel/fs/schfs/space.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 //
 // SchFS space manager: which blocks are in use.
 //

kernel/fs/schfs/vfs.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 //
 // SchFS behind the VFS: the fs_ops table that makes SchFS files reachable
 // through open(2), read(2), write(2) and the rest.

kernel/fs/schfs/vol.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 //
 // SchFS volume layer: the uberblock ring.
 //