docs: switch documentation to CC BY-NC 4.0 license

[tanghao-xiaomi]

Summary

Switch the docs repository license from Apache 2.0 to a dual-license scheme, effective May 13, 2026.

Changes

• LICENSE: Replaced Apache 2.0 stub with the full CC BY-NC 4.0 International legal text, with a copyright header identifying Xiaomi Corporation
• LICENSING.md / LICENSING_zh-cn.md: Added new bilingual documents explaining the dual-license scheme
• README.md / README_zh-cn.md: Updated the licensing section to reference the new policy
• CONTRIBUTING.md / CONTRIBUTING_zh-cn.md: Added dual-license notice for contributors so the CLA path stays consistent with the new LICENSE

Licensing Policy

Effective May 13, 2026, the docs repository adopts a dual-licensing scheme:

Content Type	License
Documentation text (Markdown files, images, diagrams)	CC BY-NC 4.0
Code samples, configuration files, scripts	Apache 2.0

Content committed before this date remains under Apache 2.0 as originally contributed.

Rationale

• Documentation is now under CC BY-NC 4.0 to prevent unauthorized commercial redistribution of openvela's written materials, while still allowing the community to translate and adapt content (which a NoDerivatives variant would forbid)
• Code samples remain under Apache 2.0 so developers can freely copy and adapt them (consistent with the rest of openvela's codebase)
• Contributor guidance is updated in CONTRIBUTING.md so submitters know exactly what license terms apply to their contributions

Legal Confirmation

Legal has reviewed and approved this change, with the guidance that the transition should be clearly demarcated by date.

Notes

• Other openvela repositories (nuttx, apps, frameworks, vendor, etc.) are not affected — they continue under their own existing licenses
• Third-party content retains its original licenses per Third_Party_and_Open_Source_Components.md