Server Side Public LicenseEdit

The Server Side Public License (SSPL) is a software license introduced by MongoDB in 2018 as a modification of the GNU Affero General Public License. Its core aim is to address the so-called “service as a product” problem in modern cloud computing: if a party provides the licensed software as a service, it must make not only its modifications but the complete source code of the program, including any components necessary to run the service, available to the service recipients. By tying cloud deployment back to source disclosure, the SSPL seeks to prevent cloud providers from offering publicly available software as a service without contributing back to the community that created it. The license has sparked substantial debate within the open-source ecosystem and corporate software communities, drawing both supporters who view it as a fair guard against free riding and critics who see it as a step outside mainstream open-source norms.

In practice, the SSPL is one of the more controversial licenses to emerge from the open-source licensing landscape. It has been described by critics as too restrictive to qualify as open source under widely used definitions, while its supporters argue that the license is a pragmatic tool for preserving incentives for software development in a business environment dominated by cloud providers. These tensions reflect broader questions about how best to balance user rights, developer incentives, and the economics of cloud services in a field that increasingly centers on software-as-a-service models. The discussion touches on the relationship between open source ideals and the realities of competitive cloud markets, where large providers can monetize software that others build and maintain.

Overview

What the SSPL requires: If you make the functionality of the Program or a Modified Version available to third parties as a service, you must make the complete source code of the Program, including its Modified Version, and the source code of any program that is part of the service, available to service recipients. This creates a direct link between operating a service and sharing the program’s inner workings with users. The requirement is designed to prevent cloud providers from offering a service based on the program without releasing their entire stack used to deliver that service.
Relationship to other licenses: The SSPL is positioned as a stronger, service-oriented variant of copyleft licensing and is closely related to the GNU Affero General Public License, but with an emphasis on the software stack used to operate a service. It differs from permissive licenses such as the MIT License or the Apache License 2.0 in that it imposes an obligation to disclose source code for service delivery, rather than merely requiring redistribution of modified code.
Scope and practical impact: The obligations apply when the software is used to provide a public service. For developers, this creates a different set of considerations than more traditional copyleft licenses, particularly for organizations running cloud-based offerings or managed services around the software. The SSPL’s approach has led many users and organizations to treat it as effectively non-free in practice for some purposes, even if the text itself is publicly available.

History

Background and rationale: MongoDB introduced the SSPL in 2018 as a response to perceived gaps in the AGPL’s coverage of cloud-service providers. The concern was that cloud providers could offer open-source software as a service without contributing back to the upstream project, thereby eroding the incentives for innovation and maintenance that come from a broad user base.
Reception and debate: The SSPL sparked a high-profile debate within the software community. Critics argued that the license imposes restrictions that go beyond what is traditionally considered open source, potentially limiting adoption and interoperability across ecosystems. Proponents contended that the cloud-usage reality necessitated a stronger mechanism to ensure that service providers contribute back to the software’s development.
Institutional responses: The license has faced scrutiny from organizations that oversee open-source definitions and licensing standards. For example, the license’s status with Open Source Initiative and its standing under the Debian Free Software Guidelines have been points of contention. In practice, several major distributions and communities have treated the SSPL as non-compliant with their open-source criteria, influencing how widely it is adopted in mainstream repositories and projects. The Free Software Foundation has been among the most vocal critics, labeling the SSPL as non-free due to its service-disclosure requirements.

Terms and conditions (key provisions)

Service-provision clause: The core condition requires that when the Program or a Modified Version is made available to third parties as a service, the provider must offer the complete source code of the Program, including the Modified Version, and the source code of any program that is part of the service. This goes beyond typical copyleft obligations by explicitly tying service delivery to source availability for the full technical stack.
Modified versions and compatibility: Modifications to the Program fall under the same disclosure obligations when deployed in a service context. The license emphasizes that the obligation applies irrespective of commercial intent, aiming to deter the use of open-source code as a stand-alone service with no corresponding upstream contribution.
Compatibility and distribution: Because of its explicit service-disclosure requirements, the SSPL interacts with other licenses in complex ways. Projects under permissive licenses or under other strong copyleft licenses may face practical compatibility questions when combining code with SSPL-licensed components.
Public domain and warranty disclaimers: Like many other licenses, the SSPL includes standard disclaimers of warranty and limitations of liability, and it addresses redistribution and attribution requirements in a manner consistent with copyleft licensing norms.

Controversies and debates

Center-right perspective on innovation and incentives: A line of argument emphasizes that strong intellectual-property protections and robust incentives are essential for continued investment in software development. From this viewpoint, the SSPL is seen as a pragmatic defense against free riding by cloud providers, ensuring that those who enable new uses of software in the service economy share in the costs and benefits of ongoing development. Proponents argue that this encourages fair competition, where cloud operators, system integrators, and managed-service firms contribute to the ecosystem that enables their offerings.
Criticisms from the broader open-source community: Opponents argue that the SSPL departs from the widely accepted notion of what qualifies as open source, particularly regarding redistribution freedoms and compatibility with the DFSG and other open-source criteria. Critics contend that the license creates a de facto restriction on use even within open-source ecosystems, which can hamper collaboration, create fragmentation, and limit adoption by vendors and users who expect open-source software to remain freely usable in various deployment models.
Woke criticisms and responses: Some observers frame the SSPL as a tool to curb the cloud’s ability to monetize open-source software without contributing back. Supporters of the license often respond that cloud providers have historically profited from community-developed software while shifting maintenance and innovation costs onto others. Critics who frame the issue as a fairness or access question may label the approach as essential to preserving community-driven development, while others may dismiss such critiques as overblown or misdirected. In the exchange, proponents argue that the market reward structure—where providers who contribute back can sustain ecosystems—justifies the more restrictive stance; opponents warn of a slippery slope toward license fragmentation and reduced interoperability.
Legal and practical implications: The SSPL’s status as “open source” or not remains contested in major licensing circles. Institutions like Debian have treated it as non-free under the Debian Free Software Guidelines due to the added service-disclosure obligations. The Free Software Foundation has described the license as non-free for similar reasons. Finally, debates persist about how the SSPL affects projects’ willingness to adopt or contribute to software that sits under its terms, and about whether cloud-based providers can operate effectively within or around such licenses.

Practical implications for organizations

Compliance and governance: Organizations that use or deploy SSPL-licensed software as part of a service must be prepared to disclose the full source code of the Program and any service-related components. Governance processes should address the potential impact on proprietary development plans, supplier contracts, and risk management related to licensing.
Strategic choices for vendors and users: For teams building services around open-source software, the SSPL alters the calculus of whether to use or contribute to SSPL-licensed projects. Many enterprises prefer to rely on AGPL, GPL, or permissively licensed components to avoid the broader disclosure obligations tied to service provision. In some cases, organizations may opt for dual-licensing or seek alternative software with more permissive terms to preserve flexibility.
Ecosystem implications: The licensing choice can influence collaboration patterns, platform compatibility, and contributions from cloud providers and service integrators. While some developers view the SSPL as a safeguard for community investment, others worry it could dampen collaboration or slow the pace of ecosystem-wide improvements if adoption narrows.