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.
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
- Read
references/selection/decision-tree.md
- Ask clarifying questions based on the decision tree:
- Primary goal (adoption vs keeping code open)?
- Patent protection needed?
- Library or application?
- SaaS/network use?
- Provide recommendation with reasoning
- Reference notable projects using recommended license
- Offer to generate LICENSE file if desired
For License Comparison Questions
- Read
references/selection/comparison-matrix.md
- If the request mentions 木兰宽松许可证 or Mulan PSL v2, also read
references/mulan-psl-v2.md
- Compare requested licenses across key dimensions:
- Permissions (commercial use, distribution, modification)
- Conditions (attribution, copyleft, source disclosure)
- Limitations (liability, warranty)
- Highlight key differences
- Provide examples of projects using each license when available
For Compliance Review
- Read
references/compliance/compatibility.md
references/compliance/checklist.md
- Identify all licenses in the project
- Check compatibility between licenses
- Flag any copyleft licenses that may affect distribution
- Note any missing attribution or compliance gaps
- Provide actionable remediation steps
- Reference
references/compliance/common-issues.md
For License/NOTICE File Generation
- Read appropriate template from
- CRITICAL: Always use canonical license text exactly as provided
- Never modify license terms or generate license text from scratch
- Only fill in placeholders: , ,
- For NOTICE files, aggregate third-party attributions properly
- For headers, use language-appropriate comment syntax
For Mulan PSL v2 Questions
- Read
references/mulan-psl-v2.md
- 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
- 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
- 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
| Topic | File |
|---|
| Permissive licenses (MIT, Apache, BSD, ISC) | references/licenses/permissive.md
|
| Copyleft licenses (GPL, LGPL, AGPL, MPL) | references/licenses/copyleft.md
|
| Other licenses (CC, Boost, zlib) | references/licenses/specialty.md
|
| License comparison table | references/selection/comparison-matrix.md
|
| License selection guide | references/selection/decision-tree.md
|
| License compatibility rules | references/compliance/compatibility.md
|
| Compliance checklist | references/compliance/checklist.md
|
| Common compliance mistakes | references/compliance/common-issues.md
|
| LICENSE file templates | references/templates/license-files.md
|
| NOTICE file templates | references/templates/notice-files.md
|
| Source header templates | references/templates/source-headers.md
|
| Mulan PSL v2 reference and canonical text | references/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:
- Confirm the license choice
- Ask for copyright holder name and year
- Output the complete canonical license text
- Remind user to place it in repository root as or
When reviewing compliance:
- List all identified licenses
- Show compatibility analysis
- Flag any issues with severity (critical/warning/info)
- Provide specific remediation steps