Licensing dictionaries

[jamesrhester]

Assuming the copyright for all the dictionaries lies with the IUCr (separate issue actually), under what terms are the dictionaries made available? Currently we have a 2000-era IUCr policy and no licence.

This issue is related to use of the dictionaries by the EMMO project. They themselves seem happy with a CC-BY-4.0 licence.

[k00ni]

Any news here?

[jamesrhester]

Thanks for bumping this. Conversation now under way.

[merkys]

Thanks for bumping this. Conversation now under way.

It seems that a vote had taken place in COMCIFS and CC-BY has been declared the winner. Can we take this result as a sign CC-BY license now applies to dictionaries within this repository since vote announcement? It would be nice to have a LICENSE or COPYING file in the repository as is usual, or at least a mention in README.md.

A legal nitpick: there are several versions of CC-BY license. Which one of them has been had in mind in the COMCIFS discussion?

[publcif]

CC-BY-4.0

…

On 31/10/2025 13:47, Andrius Merkys wrote: A legal nitpick: there are several versions of CC-BY license. Which one of them has been had in mind in the COMCIFS discussion?

[vaitkus]

I suggest that we also include an SPDX license ID [1] comment into the individual dictionary files given that they are often distributed outside of the GitHub repository (e.g. via the IUCr website) and that there is currently no formal way in the DDLm dictionary to specify the license. It would look something like:

#\#CIF_2.0
# SPDX-License-Identifier: CC-BY-4.0
##############################################################################
#                                                                            #
#                      DDLm REFERENCE DICTIONARY                             #
#                                                                            #
##############################################################################

If this is suitable, it would be nice to do this before the next release.

[1] https://spdx.dev/learn/handling-license-info/

[jamesrhester]

I agree with adding the SPDX identifier in the comment at the top of files. As a post-VolG project, I think we should add a _dictionary.licence attribute.

[vaitkus]

I created two PRs that add the SPDX headers to dictionary files in coreCIF (#565) and pdCIF (COMCIFS/cif_pd#269) dictionary repositories as this dictionaries are nearing release. I am not sure if the same header should be applied to the other files (test files, etc.) or if a file with the CC-BY-4.0 licence text should be added to the repository (probably wouldn't hurt). @jamesrhester, @merkys any suggestions?

I raised a separate issue for the future _dictionary.licence attribute (#566).

[jamesrhester]

I think adding a LICENCE file as is done in source code repositories should be sufficient.

[merkys]

SPDX headers are really nice, thanks. Top-level LICENCE would also be great to have. The latter is sort of a bigger thing, as usually such file is taken as a sign that all files under this repository are covered by it (unless of course said files have their own license pointers).