xref: /openbmc/u-boot/Licenses/README (revision df11b0c4)
1 SPDX-License-Identifier: GPL-2.0
2 
3   U-Boot is Free Software.  It is copyrighted by Wolfgang Denk and
4 many others who contributed code (see the actual source code and the
5 git commit messages for details).  You can redistribute U-Boot and/or
6 modify it under the terms of version 2 of the GNU General Public
7 License as published by the Free Software Foundation.  Most of it can
8 also be distributed, at your option, under any later version of the
9 GNU General Public License -- see individual files for exceptions.
10 
11   NOTE! This license does *not* cover the so-called "standalone"
12 applications that use U-Boot services by means of the jump table
13 provided by U-Boot exactly for this purpose - this is merely
14 considered normal use of U-Boot, and does *not* fall under the
15 heading of "derived work" -- see file  Licenses/Exceptions  for
16 details.
17 
18   Also note that the GPL and the other licenses are copyrighted by
19 the Free Software Foundation and other organizations, but the
20 instance of code that they refer to (the U-Boot source code) is
21 copyrighted by me and others who actually wrote it.
22 -- Wolfgang Denk
23 
24 
25 Like many other projects, U-Boot has a tradition of including big
26 blocks of License headers in all files.  This not only blows up the
27 source code with mostly redundant information, but also makes it very
28 difficult to generate License Clearing Reports.  An additional problem
29 is that even the same licenses are referred to by a number of
30 slightly varying text blocks (full, abbreviated, different
31 indentation, line wrapping and/or white space, with obsolete address
32 information, ...) which makes automatic processing a nightmare.
33 
34 To make this easier, such license headers in the source files will be
35 replaced with a single line reference to Unique License Identifiers
36 as defined by the Linux Foundation's SPDX project [1].
37 
38 If a "SPDX-License-Identifier:" line references more than one Unique
39 License Identifier, then this means that the respective file can be
40 used under the terms of either of these licenses, i. e. with
41 
42 	SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause
43 
44 you can choose between GPL-2.0+ and BSD-3-Clause licensing.
45 
46 We use the SPDX Unique License Identifiers here; these are available
47 at [2].
48 
49 License identifier syntax
50 -------------------------
51 
52 1. Placement:
53 
54    The SPDX license identifier in U-Boot files shall be added at the first
55    possible line in a file which can contain a comment.  For the majority
56    or files this is the first line, except for scripts which require the
57    '#!PATH_TO_INTERPRETER' in the first line.  For those scripts the SPDX
58    identifier goes into the second line.
59 
60 |
61 
62 2. Style:
63 
64    The SPDX license identifier is added in form of a comment.  The comment
65    style depends on the file type::
66 
67       C source:	// SPDX-License-Identifier: <SPDX License Expression>
68       C header:	/* SPDX-License-Identifier: <SPDX License Expression> */
69       ASM:	/* SPDX-License-Identifier: <SPDX License Expression> */
70       scripts:	# SPDX-License-Identifier: <SPDX License Expression>
71       .rst:	.. SPDX-License-Identifier: <SPDX License Expression>
72       .dts{i}:	// SPDX-License-Identifier: <SPDX License Expression>
73 
74    If a specific tool cannot handle the standard comment style, then the
75    appropriate comment mechanism which the tool accepts shall be used. This
76    is the reason for having the "/\* \*/" style comment in C header
77    files. There was build breakage observed with generated .lds files where
78    'ld' failed to parse the C++ comment. This has been fixed by now, but
79    there are still older assembler tools which cannot handle C++ style
80    comments.
81 
82 |
83 
84 3. Syntax:
85 
86    A <SPDX License Expression> is either an SPDX short form license
87    identifier found on the SPDX License List, or the combination of two
88    SPDX short form license identifiers separated by "WITH" when a license
89    exception applies. When multiple licenses apply, an expression consists
90    of keywords "AND", "OR" separating sub-expressions and surrounded by
91    "(", ")" .
92 
93    License identifiers for licenses like [L]GPL with the 'or later' option
94    are constructed by using a "+" for indicating the 'or later' option.::
95 
96       // SPDX-License-Identifier: GPL-2.0+
97       // SPDX-License-Identifier: LGPL-2.1+
98 
99    WITH should be used when there is a modifier to a license needed.
100    For example, the linux kernel UAPI files use the expression::
101 
102       // SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note
103       // SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note
104 
105    Other examples using WITH exceptions found in the linux kernel are::
106 
107       // SPDX-License-Identifier: GPL-2.0 WITH mif-exception
108       // SPDX-License-Identifier: GPL-2.0+ WITH GCC-exception-2.0
109 
110    Exceptions can only be used with particular License identifiers. The
111    valid License identifiers are listed in the tags of the exception text
112    file.
113 
114    OR should be used if the file is dual licensed and only one license is
115    to be selected.  For example, some dtsi files are available under dual
116    licenses::
117 
118       // SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
119 
120    Examples from U-Boot for license expressions in dual licensed files::
121 
122       // SPDX-License-Identifier: GPL-2.0 OR MIT
123       // SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause
124 
125    AND should be used if the file has multiple licenses whose terms all
126    apply to use the file. For example, if code is inherited from another
127    project and permission has been given to put it in U-Boot, but the
128    original license terms need to remain in effect::
129 
130       // SPDX-License-Identifier: (GPL-2.0 WITH Linux-syscall-note) AND MIT
131 
132    Another other example where both sets of license terms need to be
133    adhered to is::
134 
135       // SPDX-License-Identifier: GPL-1.0+ AND LGPL-2.1+
136 
137 [1] http://spdx.org/
138 [2] http://spdx.org/licenses/
139 
140 Full name					SPDX Identifier	OSI Approved	File name		URI
141 =======================================================================================================================================
142 GNU General Public License v2.0 only		GPL-2.0		Y		gpl-2.0.txt		http://www.gnu.org/licenses/gpl-2.0.txt
143 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
144 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
145 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
146 eCos license version 2.0			eCos-2.0			eCos-2.0.txt		http://www.gnu.org/licenses/ecos-license.html
147 BSD 2-Clause License				BSD-2-Clause	Y		bsd-2-clause.txt	http://spdx.org/licenses/BSD-2-Clause
148 BSD 3-clause "New" or "Revised" License		BSD-3-Clause	Y		bsd-3-clause.txt	http://spdx.org/licenses/BSD-3-Clause#licenseText
149 IBM PIBS (PowerPC Initialization and		IBM-pibs			ibm-pibs.txt
150 	Boot Software) license
151 ISC License					ISC		Y		isc.txt			https://spdx.org/licenses/ISC
152 SIL OPEN FONT LICENSE (OFL-1.1)			OFL-1.1		Y		OFL.txt			https://spdx.org/licenses/OFL-1.1.html
153 X11 License					X11				x11.txt			https://spdx.org/licenses/X11.html
154