How the Microsoft Shared Source CLI License Compares to Others
The Microsoft Shared Source Common Language Infrastructure (MS-SS CLI) license governs access to Microsoft's implementation of the Common Language Infrastructure (CLI). It allows you to view, use, and modify the CLI source code primarily for internal development and reference but imposes significant restrictions on redistribution and commercial use. Unlike popular open source licenses such as MIT, GPL, or Apache, the MS-SS CLI license is more limited, making it essential to understand these differences before integrating or contributing to CLI in your project.
What makes the Microsoft Shared Source Common Language Infrastructure license unique?
The MS-SS CLI license is a shared source license from Microsoft that provides access to the CLI source code with defined limitations. Unlike permissive open source licenses, it permits you to view, use, and build the CLI source primarily for internal reference and development. Redistribution rights and commercial use are often restricted to protect Microsoft's intellectual property while promoting transparency. The license allows modifying the source code for internal purposes but generally prohibits distributing modified versions or binaries without explicit permission. This controlled sharing approach contrasts with open source licenses that grant broad freedoms for redistribution and commercial use. MS-SS CLI is not recognized as open source by the Open Source Initiative due to these restrictions.
How does the MS-SS CLI license differ from popular open source licenses?
Here is a comparison of the MS-SS CLI license with MIT, GPL, and Apache licenses based on key criteria:
| Criterion | MS-SS CLI | MIT License | GPL License | Apache License |
|---|---|---|---|---|
| Permission to redistribute | Limited or restricted | Permissive, unrestricted | Requires derivative works to be GPL licensed | Permissive with patent protections |
| Commercial use | Often restricted | Allowed without restriction | Allowed but derivative works must comply with GPL | Allowed without restriction |
| Source code modification | Allowed for internal use only | Allowed and encouraged | Allowed with copyleft requirements | Allowed and encouraged |
| Copyleft (share-alike) | No | No | Yes | No |
Unlike MIT or Apache, MS-SS CLI does not grant broad rights to redistribute or use the code commercially. Compared to GPL, it is less about enforcing copyleft and more about limiting distribution and usage scenarios. Its main obligation is to restrict use to Microsoft's defined cases, often prohibiting redistribution of modified source or binaries. This makes MS-SS CLI less suitable for projects seeking open collaboration or commercial reuse without constraints.
When should you consider using or avoiding the MS-SS CLI license?
Use the MS-SS CLI license if you need to study or reference Microsoft's CLI implementation for learning, debugging, or compatibility, without plans to redistribute modified versions. It fits internal enterprise environments where inspecting the CLI source code is necessary but releasing derivatives is not intended.
Avoid the license for open source projects, especially if you want to redistribute changes or combine the code with other open source components. Commercial projects that aim to redistribute or sell software based on the CLI will find MS-SS CLI restrictive due to its limits on redistribution and commercial use. In such cases, permissive licenses like MIT or Apache are more practical. The MS-SS CLI license suits scenarios requiring access to Microsoft's reference implementation where redistribution rights are not critical.
What are the compatibility concerns mixing MS-SS CLI with other licenses?
The MS-SS CLI license's restrictions on redistribution and commercial use create challenges when combining its code with software under other licenses. For example, integrating MS-SS CLI code with GPL-licensed code is generally incompatible because GPL requires the right to redistribute derivative works, which MS-SS CLI restricts.
Mixing MS-SS CLI code with permissive licenses like MIT or Apache also poses difficulties since those licenses allow free redistribution, conflicting with MS-SS CLI’s constraints. This incompatibility usually prevents creating a combined work that can be freely distributed.
Additionally, the license terms may limit linking or combining binaries if such actions trigger redistribution or commercial use clauses. Legal risks emerge if you distribute combined binaries or source without complying with MS-SS CLI restrictions. Therefore, thorough license review and possibly legal consultation are necessary when your project includes MS-SS CLI components alongside other licensed code.
What steps can you take to comply with the MS-SS CLI license?
To comply with the MS-SS CLI license, follow these steps:
- Review the license text carefully to understand allowed uses, especially restrictions on redistribution and commercial use.
- Use the MS-SS CLI source code only for internal development, testing, or reference unless you have explicit rights to redistribute.
- Do not distribute modified versions of the MS-SS CLI code or binaries derived from it without Microsoft’s permission.
- Keep your proprietary or open source code clearly separated from MS-SS CLI licensed code to avoid accidental license conflicts.
- Document your use of MS-SS CLI components in your project, including any restrictions you are observing.
- Verify that your planned deployment aligns with the license’s allowances for commercial use.
- Consult Microsoft’s licensing FAQ or legal resources if you have questions about your specific use case or obligations.
Following these steps helps ensure you respect the MS-SS CLI license and reduce the risk of legal or compliance issues.
Conclusion
The MS-SS CLI license allows access to Microsoft's Common Language Infrastructure source code primarily for internal reference and development without redistribution or commercial deployment rights. This makes it suitable when you need Microsoft's reference implementation but do not require broad distribution rights. For open source or commercial projects that intend to redistribute or sell software based on CLI, more permissive licenses like MIT or Apache are usually better choices. Understanding these differences early avoids legal complications and helps align your licensing strategy with your project goals. Always review the MS-SS CLI license terms carefully before proceeding.
Frequently Asked Questions
Can I redistribute modified MS-SS CLI code in my own project?
No, the MS-SS CLI license generally restricts redistribution of modified versions. You can modify and use the code internally but cannot redistribute it without explicit permission from Microsoft.
Is the MS-SS CLI license considered an open source license?
No, it does not meet the Open Source Initiative’s criteria because of its restrictions on redistribution and commercial use. It is classified as a shared source license with limited permissions.
Can I use MS-SS CLI licensed code in a commercial product?
Commercial use is generally limited by the license, especially regarding redistribution. Internal commercial use might be allowed, but distributing the CLI code or derivatives commercially usually requires additional permissions from Microsoft.
How does MS-SS CLI license affect combining code with GPL-licensed software?
The redistribution restrictions in the MS-SS CLI license conflict with GPL requirements, making them incompatible. Combining code under these licenses in a way that requires redistribution rights is legally problematic.