Metric: License characteristics

[dgkf]

Exploring some of the ways that licenses get characterized, the spdx organization characterizes licenses based on whether they are "FSF Free/Libre" and "OSI Approved"

These seem to be metadata-driven and available through these files:

• FSF approval in this document: https://spdx.github.io/fsf-api/licenses-full.json
• OSI approval in these xml documents: https://github.com/spdx/license-list-XML/tree/main/src

Other resources include:

• GitHub license api, which includes the choosealicense.com/licenses metadata: https://docs.github.com/en/rest/licenses/licenses?apiVersion=2022-11-28#get-all-commonly-used-licenses

I think we should use these to build a dataset that is shipped with the package so that we can surface some metadata about licenses.

For complete coverage of this metadata, I think we should be able to provide:

• license_is_fsf_free: logical(1L), NA if license can't be identified
• license_is_osi_approved: logical(1L), NA if license can't be identified
• license_permissions: character(n); vector of permissions from GitHub api, NA_character_ if license can't be identified
• license_conditions: character(n), vector of conditions from GitHub api, NA_character_ if license can't be identified
• license_limitations: character(n), vector of limitations from GitHub api, NA_character_ if license can't be identified