1 .. SPDX-License-Identifier: GPL-2.0
2
3 .. _kernel_licensing:
4
5 Linux kernel licensing rules
6 ============================
7
8 The Linux Kernel is provided under the terms o
9 License version 2 only (GPL-2.0), as provided
10 with an explicit syscall exception described i
11 LICENSES/exceptions/Linux-syscall-note, as des
12
13 This documentation file provides a description
14 should be annotated to make its license clear
15 It doesn't replace the Kernel's license.
16
17 The license described in the COPYING file appl
18 as a whole, though individual source files can
19 which is required to be compatible with the GP
20
21 GPL-1.0+ : GNU General Public License v1
22 GPL-2.0+ : GNU General Public License v2
23 LGPL-2.0 : GNU Library General Public Li
24 LGPL-2.0+ : GNU Library General Public Li
25 LGPL-2.1 : GNU Lesser General Public Lic
26 LGPL-2.1+ : GNU Lesser General Public Lic
27
28 Aside from that, individual files can be provi
29 e.g. one of the compatible GPL variants and al
30 permissive license like BSD, MIT etc.
31
32 The User-space API (UAPI) header files, which
33 user-space programs to the kernel are a specia
34 note in the kernel COPYING file, the syscall i
35 which does not extend the GPL requirements to
36 communicate with the kernel. Because the UAPI
37 into any source files which create an executab
38 kernel, the exception must be documented by a
39
40 The common way of expressing the license of a
41 matching boilerplate text into the top comment
42 formatting, typos etc. these "boilerplates" ar
43 tools which are used in the context of license
44
45 An alternative to boilerplate text is the use
46 Exchange (SPDX) license identifiers in each so
47 identifiers are machine parsable and precise s
48 under which the content of the file is contrib
49 identifiers are managed by the SPDX Workgroup
50 have been agreed on by partners throughout the
51 legal teams. For further information see http
52
53 The Linux kernel requires the precise SPDX ide
54 The valid identifiers used in the kernel are e
55 `License identifiers`_ and have been retrieved
56 license list at https://spdx.org/licenses/ alo
57
58 License identifier syntax
59 -------------------------
60
61 1. Placement:
62
63 The SPDX license identifier in kernel files
64 possible line in a file which can contain a
65 of files this is the first line, except for
66 '#!PATH_TO_INTERPRETER' in the first line.
67 identifier goes into the second line.
68
69 |
70
71 2. Style:
72
73 The SPDX license identifier is added in for
74 style depends on the file type::
75
76 C source: // SPDX-License-Identifier: <S
77 C header: /* SPDX-License-Identifier: <S
78 ASM: /* SPDX-License-Identifier: <S
79 scripts: # SPDX-License-Identifier: <SP
80 .rst: .. SPDX-License-Identifier: <S
81 .dts{i}: // SPDX-License-Identifier: <S
82
83 If a specific tool cannot handle the standa
84 appropriate comment mechanism which the too
85 is the reason for having the "/\* \*/" styl
86 files. There was build breakage observed wi
87 'ld' failed to parse the C++ comment. This
88 there are still older assembler tools which
89 comments.
90
91 |
92
93 3. Syntax:
94
95 A <SPDX License Expression> is either an SP
96 identifier found on the SPDX License List,
97 SPDX short form license identifiers separat
98 exception applies. When multiple licenses a
99 of keywords "AND", "OR" separating sub-expr
100 "(", ")" .
101
102 License identifiers for licenses like [L]GP
103 are constructed by using a "+" for indicati
104
105 // SPDX-License-Identifier: GPL-2.0+
106 // SPDX-License-Identifier: LGPL-2.1+
107
108 WITH should be used when there is a modifie
109 For example, the linux kernel UAPI files us
110
111 // SPDX-License-Identifier: GPL-2.0 WITH
112 // SPDX-License-Identifier: GPL-2.0+ WIT
113
114 Other examples using WITH exceptions found
115
116 // SPDX-License-Identifier: GPL-2.0 WITH
117 // SPDX-License-Identifier: GPL-2.0+ WIT
118
119 Exceptions can only be used with particular
120 valid License identifiers are listed in the
121 file. For details see the point `Exceptions
122 identifiers`_.
123
124 OR should be used if the file is dual licen
125 to be selected. For example, some dtsi fil
126 licenses::
127
128 // SPDX-License-Identifier: GPL-2.0 OR B
129
130 Examples from the kernel for license expres
131
132 // SPDX-License-Identifier: GPL-2.0 OR M
133 // SPDX-License-Identifier: GPL-2.0 OR B
134 // SPDX-License-Identifier: GPL-2.0 OR A
135 // SPDX-License-Identifier: GPL-2.0 OR M
136 // SPDX-License-Identifier: (GPL-2.0 WIT
137 // SPDX-License-Identifier: GPL-1.0+ OR
138
139 AND should be used if the file has multiple
140 apply to use the file. For example, if code
141 project and permission has been given to pu
142 original license terms need to remain in ef
143
144 // SPDX-License-Identifier: (GPL-2.0 WIT
145
146 Another other example where both sets of li
147 adhered to is::
148
149 // SPDX-License-Identifier: GPL-1.0+ AND
150
151 License identifiers
152 -------------------
153
154 The licenses currently used, as well as the li
155 kernel, can be broken down into:
156
157 1. _`Preferred licenses`:
158
159 Whenever possible these licenses should be
160 fully compatible and widely used. These li
161 directory::
162
163 LICENSES/preferred/
164
165 in the kernel source tree.
166
167 The files in this directory contain the ful
168 `Metatags`_. The file names are identical
169 identifier which shall be used for the lice
170
171 Examples::
172
173 LICENSES/preferred/GPL-2.0
174
175 Contains the GPL version 2 license text and
176
177 LICENSES/preferred/MIT
178
179 Contains the MIT license text and the requi
180
181 _`Metatags`:
182
183 The following meta tags must be available i
184
185 - Valid-License-Identifier:
186
187 One or more lines which declare which Lic
188 inside the project to reference this part
189 this is a single valid identifier, but e.
190 later' options two identifiers are valid.
191
192 - SPDX-URL:
193
194 The URL of the SPDX page which contains a
195 to the license.
196
197 - Usage-Guidance:
198
199 Freeform text for usage advice. The text
200 for the SPDX license identifiers as they
201 files according to the `License identifie
202
203 - License-Text:
204
205 All text after this tag is treated as the
206
207 File format examples::
208
209 Valid-License-Identifier: GPL-2.0
210 Valid-License-Identifier: GPL-2.0+
211 SPDX-URL: https://spdx.org/licenses/GPL-
212 Usage-Guide:
213 To use this license in source code, pu
214 tag/value pairs into a comment accordi
215 guidelines in the licensing rules docu
216 For 'GNU General Public License (GPL)
217 SPDX-License-Identifier: GPL-2.0
218 For 'GNU General Public License (GPL)
219 SPDX-License-Identifier: GPL-2.0+
220 License-Text:
221 Full license text
222
223 ::
224
225 SPDX-License-Identifier: MIT
226 SPDX-URL: https://spdx.org/licenses/MIT.
227 Usage-Guide:
228 To use this license in source code, pu
229 tag/value pair into a comment accordin
230 guidelines in the licensing rules docu
231 SPDX-License-Identifier: MIT
232 License-Text:
233 Full license text
234
235 |
236
237 2. Deprecated licenses:
238
239 These licenses should only be used for exis
240 code from a different project. These licen
241 directory::
242
243 LICENSES/deprecated/
244
245 in the kernel source tree.
246
247 The files in this directory contain the ful
248 `Metatags`_. The file names are identical
249 identifier which shall be used for the lice
250
251 Examples::
252
253 LICENSES/deprecated/ISC
254
255 Contains the Internet Systems Consortium li
256 metatags::
257
258 LICENSES/deprecated/GPL-1.0
259
260 Contains the GPL version 1 license text and
261
262 Metatags:
263
264 The metatag requirements for 'other' licens
265 requirements of the `Preferred licenses`_.
266
267 File format example::
268
269 Valid-License-Identifier: ISC
270 SPDX-URL: https://spdx.org/licenses/ISC.
271 Usage-Guide:
272 Usage of this license in the kernel fo
273 and it should solely be used for impor
274 existing project.
275 To use this license in source code, pu
276 tag/value pair into a comment accordin
277 guidelines in the licensing rules docu
278 SPDX-License-Identifier: ISC
279 License-Text:
280 Full license text
281
282 |
283
284 3. Dual Licensing Only
285
286 These licenses should only be used to dual
287 license in addition to a preferred license.
288 from the directory::
289
290 LICENSES/dual/
291
292 in the kernel source tree.
293
294 The files in this directory contain the ful
295 `Metatags`_. The file names are identical
296 identifier which shall be used for the lice
297
298 Examples::
299
300 LICENSES/dual/MPL-1.1
301
302 Contains the Mozilla Public License version
303 required metatags::
304
305 LICENSES/dual/Apache-2.0
306
307 Contains the Apache License version 2.0 lic
308 metatags.
309
310 Metatags:
311
312 The metatag requirements for 'other' licens
313 requirements of the `Preferred licenses`_.
314
315 File format example::
316
317 Valid-License-Identifier: MPL-1.1
318 SPDX-URL: https://spdx.org/licenses/MPL-
319 Usage-Guide:
320 Do NOT use. The MPL-1.1 is not GPL2 co
321 dual-licensed files where the other li
322 If you end up using this it MUST be us
323 license using "OR".
324 To use the Mozilla Public License vers
325 tag/value pair into a comment accordin
326 the licensing rules documentation:
327 SPDX-License-Identifier: MPL-1.1
328 License-Text:
329 Full license text
330
331 |
332
333 4. _`Exceptions`:
334
335 Some licenses can be amended with exception
336 which the original license does not. These
337 from the directory::
338
339 LICENSES/exceptions/
340
341 in the kernel source tree. The files in th
342 exception text and the required `Exception
343
344 Examples::
345
346 LICENSES/exceptions/Linux-syscall-note
347
348 Contains the Linux syscall exception as doc
349 file of the Linux kernel, which is used for
350 e.g. /\* SPDX-License-Identifier: GPL-2.0 W
351
352 LICENSES/exceptions/GCC-exception-2.0
353
354 Contains the GCC 'linking exception' which
355 independent of its license against the comp
356 with this exception. This is required for c
357 from source code which is not compatible wi
358
359 _`Exception Metatags`:
360
361 The following meta tags must be available i
362
363 - SPDX-Exception-Identifier:
364
365 One exception identifier which can be use
366 identifiers.
367
368 - SPDX-URL:
369
370 The URL of the SPDX page which contains a
371 to the exception.
372
373 - SPDX-Licenses:
374
375 A comma separated list of SPDX license id
376 exception can be used.
377
378 - Usage-Guidance:
379
380 Freeform text for usage advice. The text
381 examples for the SPDX license identifiers
382 source files according to the `License id
383
384 - Exception-Text:
385
386 All text after this tag is treated as the
387
388 File format examples::
389
390 SPDX-Exception-Identifier: Linux-syscall
391 SPDX-URL: https://spdx.org/licenses/Linu
392 SPDX-Licenses: GPL-2.0, GPL-2.0+, GPL-1.
393 Usage-Guidance:
394 This exception is used together with o
395 to mark user-space API (uapi) header f
396 into non GPL compliant user-space appl
397 To use this exception add it with the
398 identifiers in the SPDX-Licenses tag:
399 SPDX-License-Identifier: <SPDX-Licen
400 Exception-Text:
401 Full exception text
402
403 ::
404
405 SPDX-Exception-Identifier: GCC-exception
406 SPDX-URL: https://spdx.org/licenses/GCC-
407 SPDX-Licenses: GPL-2.0, GPL-2.0+
408 Usage-Guidance:
409 The "GCC Runtime Library exception 2.0
410 of the above SPDX-Licenses for code im
411 library.
412 To use this exception add it with the
413 identifiers in the SPDX-Licenses tag:
414 SPDX-License-Identifier: <SPDX-Licen
415 Exception-Text:
416 Full exception text
417
418
419 All SPDX license identifiers and exceptions mu
420 in the LICENSES subdirectories. This is requir
421 verification (e.g. checkpatch.pl) and to have
422 and extract right from the source, which is re
423 organizations, e.g. the `FSFE REUSE initiative
424
425 _`MODULE_LICENSE`
426 -----------------
427
428 Loadable kernel modules also require a MODU
429 neither a replacement for proper source cod
430 (SPDX-License-Identifier) nor in any way re
431 determining the exact license under which t
432 is provided.
433
434 The sole purpose of this tag is to provide
435 whether the module is free software or prop
436 module loader and for user space tools.
437
438 The valid license strings for MODULE_LICENS
439
440 ============================= ============
441 "GPL" Module is li
442 does not exp
443 GPL-2.0-only
444 license info
445 via the lice
446 correspondin
447
448 "GPL v2" Same as "GPL
449 reasons.
450
451 "GPL and additional rights" Historical v
452 module sourc
453 GPL v2 varia
454 not use in n
455
456 "Dual MIT/GPL" The correct
457 module is du
458 variant or M
459
460 "Dual BSD/GPL" The module i
461 variant or B
462 variant of t
463 determined v
464 in the corre
465
466 "Dual MPL/GPL" The module i
467 variant or M
468 choice. The
469 license can
470 license info
471 source files
472
473 "Proprietary" The module i
474 This string
475 party module
476 which have t
477 tree. Module
478 the kernel w
479 the kernel m
480 modules agai
481 with EXPORT_
482 ============================= ============
483
484
485
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.