First published on Skala Legal Skills

Legal Disclaimer#

This skill is provided for informational and educational purposes only and does not constitute legal advice. The analysis and information provided should not be relied upon as a substitute for consultation with a qualified attorney. No attorney-client relationship is created by using this skill. Open source licensing involves complex legal considerations that may vary by jurisdiction. Laws and regulations vary by jurisdiction and change over time. Always consult with a licensed attorney in your jurisdiction for advice on specific legal matters. The creators and publishers of this skill disclaim any liability for actions taken or not taken based on the information provided.

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Open Source License Skill#

Comprehensive guidance for open source license selection, compliance review, and documentation drafting.

Capabilities#

1. License Selection#

Help users choose the right license based on their goals using the decision tree.

2. License Comparison#

Explain differences between licenses, compatibility, and trade-offs.

3. Compliance Review#

Analyze projects for license compliance issues and compatibility conflicts.

4. License Drafting#

Generate LICENSE files, NOTICE files, and source file headers using canonical texts.

5. Mulan PSL v2 Guidance#

Explain 木兰宽松许可证 / Mulan PSL v2, compare it with MIT or Apache-2.0, and generate canonical text or headers from the bundled reference.

Workflow#

For License Selection Questions#

1. Read references/selection/decision-tree.md
2. Ask clarifying questions based on the decision tree:
   • Primary goal (adoption vs keeping code open)?
   • Patent protection needed?
   • Library or application?
   • SaaS/network use?
3. Provide recommendation with reasoning
4. Reference notable projects using recommended license
5. Offer to generate LICENSE file if desired

For License Comparison Questions#

1. Read references/selection/comparison-matrix.md
2. If the request mentions 木兰宽松许可证 or Mulan PSL v2, also read references/mulan-psl-v2.md
3. Compare requested licenses across key dimensions:
   • Permissions (commercial use, distribution, modification)
   • Conditions (attribution, copyleft, source disclosure)
   • Limitations (liability, warranty)
4. Highlight key differences
5. Provide examples of projects using each license when available

For Compliance Review#

1. Read references/compliance/compatibility.md and references/compliance/checklist.md
2. Identify all licenses in the project
3. Check compatibility between licenses
4. Flag any copyleft licenses that may affect distribution
5. Note any missing attribution or compliance gaps
6. Provide actionable remediation steps
7. Reference references/compliance/common-issues.md for context

For License/NOTICE File Generation#

1. Read appropriate template from references/templates/
2. CRITICAL: Always use canonical license text exactly as provided
3. Never modify license terms or generate license text from scratch
4. Only fill in placeholders: [YEAR], [FULLNAME], [PROJECT NAME]
5. For NOTICE files, aggregate third-party attributions properly
6. For headers, use language-appropriate comment syntax

For Mulan PSL v2 Questions#

1. Read references/mulan-psl-v2.md
2. Explain the key traits:
   • Permissive license
   • Express copyright grant
   • Express patent grant
   • Patent retaliation clause
   • No trademark license
   • Distribution requires providing a copy of the license and retaining copyright, patent, trademark, and disclaimer notices
   • Chinese and English texts have equal legal effect, but the Chinese version prevails if they diverge
3. If the user wants to adopt Mulan PSL v2:
   • Provide the official three-step application guidance
   • Output the canonical header text when requested
   • Output the canonical license text from the bundled reference when requested
4. Compare with MIT or Apache-2.0 when helpful:
   • MIT is simpler but has no express patent grant in the text
   • Apache-2.0 and Mulan PSL v2 both include express patent language, but they are not interchangeable licenses

Reference Files#

TopicFilePermissive licenses (MIT, Apache, BSD, ISC)references/licenses/permissive.mdCopyleft licenses (GPL, LGPL, AGPL, MPL)references/licenses/copyleft.mdOther licenses (CC, Boost, zlib)references/licenses/specialty.mdLicense comparison tablereferences/selection/comparison-matrix.mdLicense selection guidereferences/selection/decision-tree.mdLicense compatibility rulesreferences/compliance/compatibility.mdCompliance checklistreferences/compliance/checklist.mdCommon compliance mistakesreferences/compliance/common-issues.mdLICENSE file templatesreferences/templates/license-files.mdNOTICE file templatesreferences/templates/notice-files.mdSource header templatesreferences/templates/source-headers.mdMulan PSL v2 reference and canonical textreferences/mulan-psl-v2.md

Key Rules#

Never Generate License Text#

Always use canonical license text from templates. License texts are legal documents that must be exact. Do not:

• Paraphrase license terms
• Generate license text from memory
• Modify standard license language
• Create "custom" licenses

Include Project Examples#

When discussing licenses, mention notable projects that use them:

• MIT: React, Node.js, jQuery, Rails, Angular
• Apache-2.0: Kubernetes, TensorFlow, Android, Spark
• GPL-3.0: WordPress, GIMP, Bash
• AGPL-3.0: Nextcloud, Mastodon, Grafana
• BSD-3-Clause: Django, Flask, numpy
• MPL-2.0: Firefox, Thunderbird
• Mulan PSL v2: Mention that it is widely used in Chinese open source ecosystems when relevant, and prefer describing characteristics over naming projects unless you are certain of a well-known example.

Flag Complex Scenarios#

Recommend legal counsel for:

• Dual licensing strategies
• License changes mid-project
• Commercial projects with copyleft dependencies
• AGPL in SaaS environments
• Multi-jurisdictional distribution
• Patent-sensitive situations

Quick Answers#

"What license should I use?"#

→ Follow decision tree; default to MIT for simplicity or Apache-2.0 for patent protection.

"Can I use GPL code in my proprietary app?"#

→ Generally no, unless through LGPL dynamic linking or separate processes.

"What's the difference between MIT and Apache-2.0?"#

→ Apache-2.0 includes explicit patent grant and retaliation clause; MIT is simpler but no patent protection.

"What's the difference between Apache-2.0 and Mulan PSL v2?"#

→ Both are permissive and include express patent language, but Mulan PSL v2 uses its own text and bilingual Chinese/English form, with the Chinese version prevailing if the two diverge.

"Is Apache-2.0 compatible with GPL?"#

→ Apache-2.0 is compatible with GPL-3.0, but NOT with GPL-2.0.

"Do I need to open source my code if I use AGPL?"#

→ Only if you modify the AGPL code AND provide it as a network service. Using unmodified AGPL tools internally doesn't trigger copyleft.

Output Format#

When generating LICENSE files:

1. Confirm the license choice
2. Ask for copyright holder name and year
3. Output the complete canonical license text
4. Remind user to place it in repository root as LICENSE or LICENSE.txt

When reviewing compliance:

1. List all identified licenses
2. Show compatibility analysis
3. Flag any issues with severity (critical/warning/info)
4. Provide specific remediation steps