sdbfs: relicense lib to LGPL v2.1

The userspace and kernel binaries are kept as GPL v2 but the library has
been relicensed as LGPL v2.1 in order to allow it to be linked to
proprietary software.

The permission to relicense the files has been approved by CERN in 2018
and then in 2021 (and also by its main author).

sdbfs/README

@@ -27,3 +27,10 @@ The thing is split in three parts
 Since SDB is used to self-describe a bus, you can even mount sdbfs
 over a real bus. In this case however only mmap is allowed on the
 individual files (no read or write method is there).
+
+
+LICENSES:
+=========
+
+* The sdbfs library is released under LGPL v2.1 license and can be included as a library into proprietary binaries.
+* The userspace tools and kernel drivers are released under GPL v2 library.
\ No newline at end of file

sdbfs/include/linux/sdb.h

 /*
  * This is the official version 1.1 of sdb.h
+ *
+ * Released to the public domain
  */
 #ifndef __SDB_H__
 #define __SDB_H__

sdbfs/lib/access.c

@@ -2,7 +2,7 @@
  * Copyright (C) 2012,2013 CERN (www.cern.ch)
  * Author: Alessandro Rubini <rubini@gnudd.com>
  *
- * Released according to the GNU GPL, version 2 or any later version.
+ * Released according to GNU LGPL, version 2.1 or any later
  *
  * This work is part of the White Rabbit project, a research effort led
  * by CERN, the European Institute for Nuclear Research.

sdbfs/lib/glue.c

@@ -2,7 +2,7 @@
  * Copyright (C) 2012,2014 CERN (www.cern.ch)
  * Author: Alessandro Rubini <rubini@gnudd.com>
  *
- * Released according to the GNU GPL, version 2 or any later version.
+ * Released according to GNU LGPL, version 2.1 or any later
  *
  * This work is part of the White Rabbit project, a research effort led
  * by CERN, the European Institute for Nuclear Research.

sdbfs/lib/libsdbfs.h

+/*
+ * Copyright (C) 2012,2014 CERN (www.cern.ch)
+ * Author: Alessandro Rubini <rubini@gnudd.com>
+ *
+ * Released according to GNU LGPL, version 2.1 or any later
+ *
+ */
+
 #ifndef __LIBSDBFS_H__
 #define __LIBSDBFS_H__
 
+
 /* The library can work in different environments, take care of them */
 #ifdef __KERNEL__
 #  include "libsdbfs-kernel.h"