SPDX-License-Identifier: GPL-2.0
U-Boot is Free Software. It is copyrighted by Wolfgang Denk and
many others who contributed code (see the actual source code and the
git commit messages for details). You can redistribute U-Boot and/or
modify it under the terms of version 2 of the GNU General Public
License as published by the Free Software Foundation. Most of it can
also be distributed, at your option, under any later version of the
GNU General Public License -- see individual files for exceptions.
NOTE! This license does *not* cover the so-called "standalone"
applications that use U-Boot services by means of the jump table
provided by U-Boot exactly for this purpose - this is merely
considered normal use of U-Boot, and does *not* fall under the
heading of "derived work" -- see file Licenses/Exceptions for
details.
Also note that the GPL and the other licenses are copyrighted by
the Free Software Foundation and other organizations, but the
instance of code that they refer to (the U-Boot source code) is
copyrighted by me and others who actually wrote it.
-- Wolfgang Denk
Like many other projects, U-Boot has a tradition of including big
blocks of License headers in all files. This not only blows up the
source code with mostly redundant information, but also makes it very
difficult to generate License Clearing Reports. An additional problem
is that even the same licenses are referred to by a number of
slightly varying text blocks (full, abbreviated, different
indentation, line wrapping and/or white space, with obsolete address
information, ...) which makes automatic processing a nightmare.
To make this easier, such license headers in the source files will be
replaced with a single line reference to Unique License Identifiers
as defined by the Linux Foundation's SPDX project [1].
If a "SPDX-License-Identifier:" line references more than one Unique
License Identifier, then this means that the respective file can be
used under the terms of either of these licenses, i. e. with
SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause
you can choose between GPL-2.0+ and BSD-3-Clause licensing.
We use the SPDX Unique License Identifiers here; these are available
at [2].
License identifier syntax
-------------------------
1. Placement:
The SPDX license identifier in U-Boot files shall be added at the first
possible line in a file which can contain a comment. For the majority
or files this is the first line, except for scripts which require the
'#!PATH_TO_INTERPRETER' in the first line. For those scripts the SPDX
identifier goes into the second line.
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2. Style:
The SPDX license identifier is added in form of a comment. The comment
style depends on the file type::
C source: // SPDX-License-Identifier: <SPDX License Expression>
C header: /* SPDX-License-Identifier: <SPDX License Expression> */
ASM: /* SPDX-License-Identifier: <SPDX License Expression> */
scripts: # SPDX-License-Identifier: <SPDX License Expression>
.rst: .. SPDX-License-Identifier: <SPDX License Expression>
.dts{i}: // SPDX-License-Identifier: <SPDX License Expression>
If a specific tool cannot handle the standard comment style, then the
appropriate comment mechanism which the tool accepts shall be used. This
is the reason for having the "/\* \*/" style comment in C header
files. There was build breakage observed with generated .lds files where
'ld' failed to parse the C++ comment. This has been fixed by now, but
there are still older assembler tools which cannot handle C++ style
comments.
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3. Syntax:
A <SPDX License Expression> is either an SPDX short form license
identifier found on the SPDX License List, or the combination of two
SPDX short form license identifiers separated by "WITH" when a license
exception applies. When multiple licenses apply, an expression consists
of keywords "AND", "OR" separating sub-expressions and surrounded by
"(", ")" .
License identifiers for licenses like [L]GPL with the 'or later' option
are constructed by using a "+" for indicating the 'or later' option.::
// SPDX-License-Identifier: GPL-2.0+
// SPDX-License-Identifier: LGPL-2.1+
WITH should be used when there is a modifier to a license needed.
For example, the linux kernel UAPI files use the expression::
// SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note
// SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note
Other examples using WITH exceptions found in the linux kernel are::
// SPDX-License-Identifier: GPL-2.0 WITH mif-exception
// SPDX-License-Identifier: GPL-2.0+ WITH GCC-exception-2.0
Exceptions can only be used with particular License identifiers. The
valid License identifiers are listed in the tags of the exception text
file.
OR should be used if the file is dual licensed and only one license is
to be selected. For example, some dtsi files are available under dual
licenses::
// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
Examples from U-Boot for license expressions in dual licensed files::
// SPDX-License-Identifier: GPL-2.0 OR MIT
// SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause
AND should be used if the file has multiple licenses whose terms all
apply to use the file. For example, if code is inherited from another
project and permission has been given to put it in U-Boot, but the
original license terms need to remain in effect::
// SPDX-License-Identifier: (GPL-2.0 WITH Linux-syscall-note) AND MIT
Another other example where both sets of license terms need to be
adhered to is::
// SPDX-License-Identifier: GPL-1.0+ AND LGPL-2.1+
[1] http://spdx.org/
[2] http://spdx.org/licenses/
Full name SPDX Identifier OSI Approved File name URI
=======================================================================================================================================
GNU General Public License v2.0 only GPL-2.0 Y gpl-2.0.txt http://www.gnu.org/licenses/gpl-2.0.txt
GNU General Public License v2.0 or later GPL-2.0+ Y gpl-2.0.txt http://www.gnu.org/licenses/gpl-2.0.txt
GNU Library General Public License v2 or later LGPL-2.0+ Y lgpl-2.0.txt http://www.gnu.org/licenses/old-licenses/lgpl-2.0.txt
GNU Lesser General Public License v2.1 or later LGPL-2.1+ Y lgpl-2.1.txt http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt
eCos license version 2.0 eCos-2.0 eCos-2.0.txt http://www.gnu.org/licenses/ecos-license.html
BSD 2-Clause License BSD-2-Clause Y bsd-2-clause.txt http://spdx.org/licenses/BSD-2-Clause
BSD 3-clause "New" or "Revised" License BSD-3-Clause Y bsd-3-clause.txt http://spdx.org/licenses/BSD-3-Clause#licenseText
IBM PIBS (PowerPC Initialization and IBM-pibs ibm-pibs.txt
Boot Software) license
ISC License ISC Y isc.txt https://spdx.org/licenses/ISC
SIL OPEN FONT LICENSE (OFL-1.1) OFL-1.1 Y OFL.txt https://spdx.org/licenses/OFL-1.1.html
X11 License X11 x11.txt https://spdx.org/licenses/X11.html