bip3: Switch to SPDX identifiers #1892

real-or-random · 2025-07-09T09:18:17Z

This has been discussed in #1819 (review)

See individual commit messages for further rationale. I can squash the commits if this will be cleaner.

This doesn't touch all the "License" and "License-Code" headers yet. Let's first agree on the changes, and then we can implement them.

real-or-random · 2025-07-09T09:57:22Z

After staring at this section and some BIP preambles for a while, a further suggestion is to drop "License-Code" entirely. It's used only by five BIPs so far (BIP 98, BIP 116, BIP 117, BIP 330, BIP 340), and I think it creates more ambiguity than it tries to resolve:

For BIP98, BIP116, and BIP 117 (some comments below apply to all of them but I list them only once):

BIP98 contains "source code" to render a diagram used in the document. Is this covered by "License" or by "License-Code"?
In fact, all aux files of BIP98 are either diagrams or their source code (or a shell script to build the diagrams). I think what they meant with "All provided source code is licensed under the MIT license." in the copyright section is that the reference implementation of the BIP is under MIT, but this reference implementation lives in another repo, which anyway has an explicit MIT license file as fork of Bitcoin Core.
BIP 116 contains a Bitcoin script. I claim that this is source code. Is it covered by "License" or by "License-Code"?

BIP330:

The Copyright section just says: "This document is licensed under the Creative Commons CC0 1.0 Universal license.", not talking about a different license (MIT) for code at all. Which code should be under MIT? The implementation in a PR to Bitcoin Core or this aux file?

BIP340:

The "License-Code" header was introduced only recently (by me) as part of changing the license of the code and the test vectors. But this was limited in scope to the code only to avoid obtaining permission from even more people. We should have started from scratch with everything under CC0 OR MIT.

I feel that this just relying on this text in BIP3 would be a sufficient solution (here in the version after this PR but the one before was also good):

Each auxiliary source code file or source directory should specify the license under which it is made available as is
common in software (e.g., with a SPDX-License-Identifier: <SPDX License Expression> comment,
a license header, or a LICENSE/COPYING file). It is recommended to make any test vectors available under CC0-1.0 or
FSFAP in addition to any other licenses to allow anyone to copy test vectors into their implementations without
introducing license hindrances. Licenses listed in the License-Code header apply to all source directories, source code
files, and test vectors provided with the BIP except those where a LICENSE file in a directory or the file header states
otherwise.

If we stick to something like this, then licensing will be less ambiguous, and we should just drop License-Code.

It could still be rephrased a bit to say "each auxiliary code file or directory made available under different terms than what is specified in the License header" to clarify that the License header is meant to apply to all kinds of aux files, unless specified otherwise. And we'll need a note that old BIPs may have a License-Code header and simply refer to BIP2.

You could say that should belong to a larger overhaul of the legal stuff in BIP3 (see murchandamus#2 (comment) and murchandamus#2 (comment)), but I don't think that's the case. Dropping the header (only for new BIPs, of course) is purely an "editorial" thing and doesn't go into the actual legal issues, so I'd say it belongs to BIP3.

You could also say that I'm quite late with this comment, and I can't really argue against that...

murchandamus

Thanks for taking the time to put together this proposal to improve BIP 3. I heartily agree with all your suggestions including that we should drop the License-Code header for future BIPs. Thank you for taking the time to write the detailed motivations in the commit messages. I went through all the proposed changes commit by commit and support the content of all of the edits. If you touch it again, I’d request that the changes be amended to drop the reformatting of line lengths to minimize the diffs.

If you would like to add also text to drop the License-Code header I’d also support that, otherwise, I can add that as a follow-up to this PR.

bip-0003.md

SPDX doesn't have an official identifier for "public domain", at least not for the simple "This document is placed into the public domain" declarations used in some BIPs, see https://wiki.spdx.org/view/Legal_Team/Decisions/Dealing_with_Public_Domain_within_SPDX_Files for the rationale provided by their legal team. The rationale is sound, but It's possible to create "user-defined" identifiers of the form LicenseRef-X. This is a good idea here to make sure that all SPDX expression will be formally valid. And in our case, all "PD" BIPs match the following pseudo regex, so there's not much potential for confusion: "This (document|BIP|work|proposal) is (hereby)? (placed)? in the public domain." So it makes sense to keep using a single identifier for all of these.

That's a bit of legal nitpicking, sorry. CC0 contains something like a public domain dedication along with a fallback license, so it's neither entirely. Some call it a "legal instrument". I prefer not calling it anything.

I think that requirement is not helpful. I don't think hat including additional licenses will be overwhelming to the reader. If anything, it will obfuscates the actual licensing conditions. (Anyway, this should be super rare.)

The actual reason why I suggest this is that I think that's a great default choice for a new BIP, so it's a perfect example. CC0-1.0 is a great liberal choice for the BIP document (and test vectors etc.), and MIT is the common choice for code in our ecosystem. Putting both BIP and code under the "OR" avoids any confusion about which part is licensed under which terms and also avoids any hassle when reorganizing, e.g., when moving code out of the BIP Markdown file to a separate file etc. But I don't want this PR to recommend a license, so let me sell this change as an editorial change to an example, which is warranted because the MIT is much more known than FSFAP, in particular in this ecosystem.

real-or-random · 2025-07-18T11:52:46Z

Sorry for the changing line breaks! I don't like this either, but the line breaks were so consistent that I assumed you wanted me to reformat... I changed it back (first force-push to a50e1ca) and also added a change to the "Header Descriptions" section, which I had overlooked (second force-push to 88d2918).

As a side note, what I highly recommend for new texts and BIPs is Semantic Line Breaks (also called Semantic Linefeeds or Ventilated Prose), i.e., having a line break after each substantial unit of thought. This makes it so much easier to reorganize thoughts during editing, and it also keeps the diffs clean. A similar, but slightly worse (if you ask me) advice is having full sentence per line, see also here.

If you would like to add also text to drop the License-Code header I’d also support that, otherwise, I can add that as a follow-up to this PR.

I'm happy to take care of it next week. I suggest a follow-up PR because this PR is ready from my side now. But I can also add commits here if you prefer that. Just let me know.

jonatack

ACK 88d2918

A few minor comments that can be done in a follow-up (along with dropping the License-Code header).

jonatack · 2025-07-18T20:09:38Z

bip-0003.md

 * CC0-1.0: [Creative Commons CC0 1.0 Universal](https://creativecommons.org/publicdomain/zero/1.0/)
-* GNU-All-Permissive: [GNU All-Permissive License](http://www.gnu.org/prep/maintain/html_node/License-Notices-for-Other-Files.html)
+* FSFAP: [FSF All Permissive License](https://www.gnu.org/prep/maintain/html_node/License-Notices-for-Other-Files.html)


In commit e5748c9, maybe update the link to the more complete https://spdx.org/licenses/FSFAP.html

jonatack · 2025-07-18T20:13:39Z

bip-0003.md

-* PD: Released into the public domain
-* OPL: [Open Publication License, version 1.0](http://opencontent.org/openpub/)
+* LicenseRef-PD: Placed into the public domain
+* OPUBL-1.0: [Open Publication License 1.0](https://opencontent.org/openpub/)


In commit 85a248f, maybe update the link to the more comprehensive https://spdx.org/licenses/OPUBL-1.0.html

jonatack · 2025-07-18T20:30:01Z

bip-0003.md

 or the file header states otherwise.

 For example, a preamble specifying the optional License-Code header might look like:

    License:         CC0-1.0
    License-Code:    MIT

-In this case, the code in the BIP is not available under CC0-1.0, but is only available under the terms of the MIT
+In this case, the source code in the BIP is not available under Creative Commons CC0 1.0 Universal, but is only available under the MIT


In commit 0cc4d26, nit, per https://spdx.org/licenses/CC0-1.0.html

Suggested change

In this case, the source code in the BIP is not available under Creative Commons CC0 1.0 Universal, but is only available under the MIT

In this case, the source code in the BIP is not available under Creative Commons Zero v1.0 Universal, but is only available under the MIT

jonatack · 2025-07-18T20:31:56Z

bip-0003.md


 #### Not Acceptable Licenses

 All licenses not explicitly included in the above lists are not acceptable terms for a Bitcoin Improvement Proposal.
-However, BIPs predating this proposal were allowed under other terms, and should use these abbreviations
-when no other license is granted:
+However, BIPs predating this proposal were accepted under other terms, and should use one the following identifiers.


In commit 0cc4d26, missing word

Suggested change

However, BIPs predating this proposal were accepted under other terms, and should use one the following identifiers.

However, BIPs predating this proposal were accepted under other terms, and should use one of the following identifiers.

real-or-random force-pushed the 202507-spdx branch 2 times, most recently from 7cf70ec to 6183adb Compare July 9, 2025 09:33

real-or-random force-pushed the 202507-spdx branch from 6183adb to d67d444 Compare July 9, 2025 10:02

real-or-random mentioned this pull request Jul 9, 2025

Process: Activate BIP3 #1820

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jonatack added Proposed BIP modification PR Author action required Needs updates, has unaddressed review comments, or is otherwise waiting for PR author labels Jul 15, 2025

real-or-random force-pushed the 202507-spdx branch from d67d444 to a50e1ca Compare July 18, 2025 11:18

real-or-random added 10 commits July 18, 2025 13:29

bip3: Switch to SPDX License Expressions

c3b6691

bip3: Fix SPDX id of FSF/GNU All Permissive

e5748c9

bip3: Fix SPDX id of Open Publication License

85a248f

bip3: Don't call CC0 a license

d01e941

That's a bit of legal nitpicking, sorry. CC0 contains something like a public domain dedication along with a fallback license, so it's neither entirely. Some call it a "legal instrument". I prefer not calling it anything.

bip3: Don't require omitting unacceptable licenses

3de6ed6

I think that requirement is not helpful. I don't think hat including additional licenses will be overwhelming to the reader. If anything, it will obfuscates the actual licensing conditions. (Anyway, this should be super rare.)

bip3: Recommend SPDX-License-Identifier comments

e1d72f0

bip3: Editorial changes in "BIP Licensing"

0cc4d26

bip3: Editorial cleanup of the license lists

88d2918

real-or-random force-pushed the 202507-spdx branch from a50e1ca to 88d2918 Compare July 18, 2025 11:29

jonatack reviewed Jul 18, 2025

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jonatack merged commit 340c1a3 into bitcoin:master Jul 18, 2025
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jonatack removed the PR Author action required Needs updates, has unaddressed review comments, or is otherwise waiting for PR author label Jul 18, 2025

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bip3: Switch to SPDX identifiers #1892

bip3: Switch to SPDX identifiers #1892

real-or-random commented Jul 9, 2025

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	In this case, the source code in the BIP is not available under Creative Commons CC0 1.0 Universal, but is only available under the MIT
	In this case, the source code in the BIP is not available under Creative Commons Zero v1.0 Universal, but is only available under the MIT

	However, BIPs predating this proposal were accepted under other terms, and should use one the following identifiers.
	However, BIPs predating this proposal were accepted under other terms, and should use one of the following identifiers.

bip3: Switch to SPDX identifiers #1892

bip3: Switch to SPDX identifiers #1892

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