What You May Actually Do

The licenses you will meet.

Public domain or CC0: use freely; attribution is still courteous.

CC BY: attribution required.

CC BY-SA: attribution required, and derived work carries the same license.

CC BY-NC: no commercial use, and the definition is broader than people assume.

No license stated: this does not mean free to use. It means you have no permission and should ask.

Separately, terms of service can restrict scraping and redistribution regardless of the license on the data itself. Both apply.

Attribution is cheap and specific. Name the publisher, link to the source, state the license, and give the date you fetched it. Four facts, one line, and it converts your project from something that borrowed data into something that cites it.