Add ADR002: Use CC BY-SA 4.0 License

Author: jhagberg

docs/decisions/0002-use-cc-by-sa-4-0-license.md

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+# 2. Use CC BY-SA 4.0 License
+
+Date: 2025-11-25
+
+## Status
+
+Accepted
+
+## Context
+
+We need to choose an appropriate license for this architecture documentation repository. The documentation will contain:
+- Architecture Decision Records (ADRs)
+- Process documentation
+- Technical governance guidelines
+- Standards and best practices
+
+The license should:
+- Allow others to learn from and adapt our architectural decisions
+- Ensure that derivative works remain open and accessible
+- Require attribution to SciLifeLab
+- Be compatible with collaborative development via GitHub issues and pull requests
+
+## Decision
+
+We will use the Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license for this repository.
+
+## Consequences
+
+### Positive
+
+- **Share-alike provision**: Any derivative works must be distributed under the same or compatible license, ensuring the documentation remains open
+- **Attribution requirement**: Users must give appropriate credit, which helps maintain visibility of SciLifeLab's contributions
+- **Wide adoption**: CC BY-SA 4.0 is widely recognized and understood in the open-source community (used by Wikipedia and many documentation projects)
+- **Flexibility**: Others can freely use, adapt, and build upon our architectural decisions while keeping them accessible
+- **Non-software focus**: CC licenses are specifically designed for creative works and documentation, making them more appropriate than software licenses (MIT, GPL, etc.)
+
+### Negative
+
+- **Not suitable for code**: Any code examples should be licensed separately under a software license
+- **Compatibility considerations**: Share-alike requirement may limit how others can combine our documentation with other licensed content
+- **No warranty disclaimer**: Users should be aware that architectural decisions are provided "as-is" without guarantees of suitability
+
+### Neutral
+
+- The license file (LICENSE) has been added to the repository root
+- A license badge and information have been added to the README
+- Future code repositories may need different licenses (e.g., MIT, Apache 2.0) appropriate for software
+