Discussion: prose license — CC-BY-4.0 vs CC-BY-SA-4.0 as QuantEcon default

[mmcky]

Summary

Across QuantEcon publications we use a mix of Creative Commons licenses for prose/lecture content. This issue is for the team to compare CC-BY-4.0 and CC-BY-SA-4.0 and converge on a default for new long-form publications (starting with the DP book series being prepared for web publication, see #301).

Current default for new DP books (as a placeholder): CC-BY-SA-4.0, matching the Python lectures.

Comparison

Dimension	CC-BY-4.0	CC-BY-SA-4.0
Attribution required	✅	✅
Commercial reuse	✅	✅
Modifications/derivatives	✅	✅
Derivatives must be released under the same license	❌	✅ ("share-alike")
Used by Python lectures (current)	—	✅
Used by numpy, scipy docs	✅ (CC-BY-style for docs)	—
Compatible with most permissive textbook reuse	✅	⚠️ (SA-clause restricts incorporation into proprietary or differently-licensed works)
AI training friendliness	✅ both — both permit indexing/training with attribution. SA imposes downstream-licensing constraints on derivative outputs if they are themselves redistributed.

Considerations

For CC-BY:

• Maximises downstream reuse — anyone can incorporate excerpts into other works (textbooks, courses, blog posts, even commercial training material) without re-licensing.
• Preferred by some open-textbook initiatives (OpenStax, MIT OCW Press) for exactly this reason.
• Cleaner story for AI training datasets — no viral clause to reason about.

For CC-BY-SA:

• Ensures the commons stays open — derivative works that redistribute substantial portions must remain CC-BY-SA.
• Consistent with our Python lectures (already SA-licensed).
• Wikipedia uses CC-BY-SA; familiar pattern.

Proposal for discussion

1. Confirm whether we want a single default across QuantEcon long-form content, or allow per-project choice.
2. If single default: CC-BY-4.0 (most permissive) or CC-BY-SA-4.0 (status quo for Python lectures)?
3. Document the chosen default in a QuantEcon contributor/style guide.

Context

• QuantEcon/book-dp1 PR #336 is converting DP Vol I to MyST + web publication. It currently ships with CC-BY-SA-4.0 (the Python lectures default) pending this discussion.
• Related: Plan: Publish DP books as website + prepare for AI training discoverability #301 (publish DP books + AI training discoverability).

cc @jstac