LICENSES/license-rules.txt

   1 # SPDX-License-Identifier: GPL-2.0-or-later OR GFDL-1.2-no-invariants-or-later
   2
   3 OpenOCD licensing rules
   4 =======================
   5
   6 The OpenOCD source code is provided under the terms of the GNU General
   7 Public License version 2 or later (GPL-2.0-or-later), as provided in
   8 LICENSES/preferred/GPL-2.0.
   9
  10 The OpenOCD documentation is provided under the terms of the GNU Free
  11 Documentation License version 1.2 or later without Invariant Sections
  12 (GFDL-1.2-no-invariants-or-later).
  13
  14 Few stand-alone applications coexist in the same code tree of OpenOCD
  15 and are provided under the terms of the GNU General Public License
  16 version 3 (GPL-3.0), as provided in LICENSES/stand-alone/GPL-3.0.
  17
  18 This documentation file provides a description of how each source file
  19 should be annotated to make its license clear and unambiguous.
  20 It doesn't replace the OpenOCD's license.
  21
  22 The license described in the COPYING file applies to the OpenOCD source
  23 as a whole, though individual source files can have a different license
  24 which is required to be compatible with the GPL-2.0:
  25
  26     GPL-1.0-or-later  : GNU General Public License v1.0 or later
  27     GPL-2.0-or-later  : GNU General Public License v2.0 or later
  28     LGPL-2.0          : GNU Library General Public License v2 only
  29     LGPL-2.0-or-later : GNU Library General Public License v2 or later
  30     LGPL-2.1          : GNU Lesser General Public License v2.1 only
  31     LGPL-2.1-or-later : GNU Lesser General Public License v2.1 or later
  32
  33 Aside from that, individual files can be provided under a dual license,
  34 e.g. one of the compatible GPL variants and alternatively under a
  35 permissive license like BSD, MIT etc.
  36
  37 The common way of expressing the license of a source file is to add the
  38 matching boilerplate text into the top comment of the file. Due to
  39 formatting, typos etc. these "boilerplates" are hard to validate for
  40 tools which are used in the context of license compliance.
  41
  42 An alternative to boilerplate text is the use of Software Package Data
  43 Exchange (SPDX) license identifiers in each source file. SPDX license
  44 identifiers are machine parsable and precise shorthands for the license
  45 under which the content of the file is contributed. SPDX license
  46 identifiers are managed by the SPDX Workgroup at the Linux Foundation and
  47 have been agreed on by partners throughout the industry, tool vendors, and
  48 legal teams. For further information see https://spdx.org/
  49
  50 OpenOCD requires the precise SPDX identifier in all source files.
  51 The valid identifiers used in OpenOCD are explained in the section
  52 `License identifiers` and have been retrieved from the official SPDX
  53 license list at https://spdx.org/licenses/ along with the license texts.
  54
  55 License identifier syntax
  56 -------------------------
  57
  58 1. Placement:
  59
  60    The SPDX license identifier in OpenOCD files shall be added at the
  61    first possible line in a file which can contain a comment. For the
  62    majority of files this is the first line, except for scripts which
  63    require the '#!PATH_TO_INTERPRETER' in the first line. For those
  64    scripts the SPDX identifier goes into the second line.
  65
  66 2. Style:
  67
  68    The SPDX license identifier is added in form of a comment. The comment
  69    style depends on the file type::
  70
  71       C source:  // SPDX-License-Identifier: <SPDX License Expression>
  72       C header:  /* SPDX-License-Identifier: <SPDX License Expression> */
  73       ASM:       /* SPDX-License-Identifier: <SPDX License Expression> */
  74       makefiles: # SPDX-License-Identifier: <SPDX License Expression>
  75       scripts:   # SPDX-License-Identifier: <SPDX License Expression>
  76       texinfo:   @c SPDX-License-Identifier: <SPDX License Expression>
  77       text:      # SPDX-License-Identifier: <SPDX License Expression>
  78
  79    If a specific tool cannot handle the standard comment style, then the
  80    appropriate comment mechanism which the tool accepts shall be used. This
  81    is the reason for having the "/\* \*/" style comment in C header
  82    files. There was build breakage observed with generated .lds files where
  83    'ld' failed to parse the C++ comment. This has been fixed by now, but
  84    there are still older assembler tools which cannot handle C++ style
  85    comments.
  86
  87 3. Syntax:
  88
  89    A <SPDX License Expression> is either an SPDX short form license
  90    identifier found on the SPDX License List, or the combination of two
  91    SPDX short form license identifiers separated by "WITH" when a license
  92    exception applies. When multiple licenses apply, an expression consists
  93    of keywords "AND", "OR" separating sub-expressions and surrounded by
  94    "(", ")" .
  95
  96    License identifiers for licenses like [L]GPL with the 'or later' option
  97    are constructed by using a "-or-later":
  98
  99       // SPDX-License-Identifier: GPL-2.0-or-later
 100       // SPDX-License-Identifier: LGPL-2.1-or-later
 101
 102    WITH should be used when there is a modifier to a license needed.
 103    Exceptions can only be used with particular License identifiers. The
 104    valid License identifiers are listed in the tags of the exception text
 105    file.
 106
 107    OR should be used if the file is dual licensed and only one license is
 108    to be selected. For example, some source files are available under dual
 109    licenses:
 110
 111       // SPDX-License-Identifier: GPL-2.0-or-later OR BSD-1-Clause
 112       // SPDX-License-Identifier: GPL-2.0-or-later OR BSD-2-Clause
 113       // SPDX-License-Identifier: GPL-2.0-or-later OR BSD-3-Clause
 114
 115    AND should be used if the file has multiple licenses whose terms all
 116    apply to use the file. For example, if code is inherited from another
 117    project and permission has been given to put it in OpenOCD, but the
 118    original license terms need to remain in effect::
 119
 120       // SPDX-License-Identifier: GPL-2.0-or-later AND MIT
 121
 122 License identifiers
 123 -------------------
 124
 125 The licenses currently used, as well as the licenses for code added to
 126 OpenOCD, can be broken down into:
 127
 128 1. `Preferred licenses`:
 129
 130    Whenever possible these licenses should be used as they are known to be
 131    fully compatible and widely used. These licenses are available from the
 132    directory:
 133
 134       LICENSES/preferred/
 135
 136    in the OpenOCD source tree.
 137
 138    The files in this directory contain the full license text and
 139    `Metatags`. The file names are identical to the SPDX license
 140    identifier which shall be used for the license in source files.
 141
 142    Examples:
 143
 144       LICENSES/preferred/GPL-2.0
 145
 146    Contains the GPL version 2 license text and the required metatags.
 147
 148    `Metatags`:
 149
 150    The following meta tags must be available in a license file:
 151
 152    - Valid-License-Identifier:
 153
 154      One or more lines which declare which License Identifiers are valid
 155      inside the project to reference this particular license text. Usually
 156      this is a single valid identifier, but e.g. for licenses with the 'or
 157      later' options two identifiers are valid.
 158
 159    - SPDX-URL:
 160
 161      The URL of the SPDX page which contains additional information related
 162      to the license.
 163
 164    - Usage-Guidance:
 165
 166      Freeform text for usage advice. The text must include correct examples
 167      for the SPDX license identifiers as they should be put into source
 168      files according to the `License identifier syntax` guidelines.
 169
 170    - License-Text:
 171
 172      All text after this tag is treated as the original license text
 173
 174    File format examples::
 175
 176       Valid-License-Identifier: GPL-2.0-only
 177       Valid-License-Identifier: GPL-2.0-or-later
 178       SPDX-URL: https://spdx.org/licenses/GPL-2.0.html
 179       Usage-Guide:
 180         To use this license in source code, put one of the following SPDX
 181         tag/value pairs into a comment according to the placement
 182         guidelines in the licensing rules documentation.
 183         For 'GNU General Public License (GPL) version 2 only' use:
 184           SPDX-License-Identifier: GPL-2.0-only
 185         For 'GNU General Public License (GPL) version 2 or any later version' use:
 186           SPDX-License-Identifier: GPL-2.0-or-later
 187       License-Text:
 188         Full license text
 189
 190 2. Exceptions:
 191
 192    Some licenses can be amended with exceptions which grant certain rights
 193    which the original license does not.  These exceptions are available
 194    from the directory::
 195
 196       LICENSES/exceptions/
 197
 198    in the OpenOCD source tree.  The files in this directory contain the full
 199    exception text and the required `Exception Metatags`_.
 200
 201    Examples::
 202
 203       LICENSES/exceptions/eCos-exception-2.0
 204
 205    Exception Metatags:
 206
 207    The following meta tags must be available in an exception file:
 208
 209    - SPDX-Exception-Identifier:
 210
 211      One exception identifier which can be used with SPDX license
 212      identifiers.
 213
 214    - SPDX-URL:
 215
 216      The URL of the SPDX page which contains additional information related
 217      to the exception.
 218
 219    - SPDX-Licenses:
 220
 221      A comma separated list of SPDX license identifiers for which the
 222      exception can be used.
 223
 224    - Usage-Guidance:
 225
 226      Freeform text for usage advice. The text must be followed by correct
 227      examples for the SPDX license identifiers as they should be put into
 228      source files according to the `License identifier syntax`_ guidelines.
 229
 230    - Exception-Text:
 231
 232      All text after this tag is treated as the original exception text
 233
 234    File format examples::
 235
 236       SPDX-Exception-Identifier: eCos-exception-2.0
 237       SPDX-URL: https://spdx.org/licenses/eCos-exception-2.0.html
 238       SPDX-Licenses: GPL-2.0-only, GPL-2.0-or-later
 239       Usage-Guide:
 240         This exception is used together with one of the above SPDX-Licenses.
 241         To use this exception add it with the keyword WITH to one of the
 242         identifiers in the SPDX-Licenses tag:
 243           SPDX-License-Identifier: <SPDX-License> WITH eCos-exception-2.0
 244       License-Text:
 245         Full license text
 246
 247 3. Stand-alone licenses:
 248
 249    These licenses should only be used for stand-alone applications that are
 250    distributed with OpenOCD but are not included in the OpenOCD binary.
 251    These licenses are available from the directory:
 252
 253      LICENSES/stand-alone/
 254
 255    in the OpenOCD source tree.
 256
 257    Examples:
 258
 259      SPDX-License-Identifier: GPL-3.0
 260
 261 The format and requirements of the license files in the other sub-directories
 262 of directory
 263
 264    LICENSES
 265
 266 have to follow the same format and requirements of the `Preferred licenses`.
 267
 268 All SPDX license identifiers and exceptions must have a corresponding file
 269 in the LICENSES subdirectories. This is required to allow tool
 270 verification (e.g. checkpatch.pl) and to have the licenses ready to read
 271 and extract right from the source, which is recommended by various FOSS
 272 organizations, e.g. the `FSFE REUSE initiative <https://reuse.software/>`.