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28.1: Open Source Licensing and Security Implications

Disclaimer: This section provides general educational information about open source licensing considerations. It does not constitute legal advice. Organizations should consult qualified legal counsel for guidance on specific licensing situations and compliance obligations.

Open source licensing and security exist in a complex relationship that most organizations underestimate. When you incorporate an open source component into your software, you're not just adopting code—you're accepting legal obligations that affect how you can modify, distribute, and secure that code. A security patch that fixes a critical vulnerability might create unexpected licensing obligations. A dependency update that resolves a security issue might introduce license incompatibilities. A contribution to fix an upstream vulnerability might require signing agreements that affect your intellectual property rights.

For organizations managing software supply chains, understanding these intersections prevents both security and legal exposure. Security teams focused solely on vulnerability remediation may inadvertently create compliance violations. Legal teams unfamiliar with security urgency may impede critical patching. The most effective approach integrates licensing awareness into security processes, ensuring that security activities comply with licensing obligations while licensing reviews don't obstruct necessary security responses.

License Type Overview

Open source licenses fall into two broad categories with fundamentally different implications for security activities.

Permissive licenses grant broad rights with minimal obligations. Users may use, modify, and distribute software under these licenses with few restrictions—typically requiring only attribution and preservation of license notices. Common permissive licenses include:

  • MIT License: Permits nearly unrestricted use with attribution
  • Apache License 2.0: Similar to MIT with additional patent grant provisions
  • BSD Licenses: Various forms permitting broad use with attribution
  • ISC License: Functionally equivalent to MIT with simpler language

For security purposes, permissive licenses generally present minimal complications. You can patch the code, distribute modified versions, and incorporate components into proprietary software without triggering extensive obligations. The primary requirement—maintaining attribution and license notices—rarely conflicts with security activities.

Copyleft licenses require that derivative works be distributed under the same license terms. When you modify copyleft-licensed code and distribute the result, you must make your modifications available under the same license. This "viral" or "reciprocal" characteristic creates more complex considerations for security activities. Major copyleft licenses include:

Understanding license categories enables appropriate handling when security needs arise. Permissive components can generally be patched and distributed without special procedures. Copyleft components require attention to derivative work definitions and source code availability obligations.

Patching Obligations Under Different Licenses

When you patch a security vulnerability in open source code, your obligations depend on the license and how you distribute the patched software.

Permissive License Patching

For permissively licensed components, patching creates minimal additional obligations:

  • Maintain original copyright notices and license text
  • Include attribution as required by the specific license
  • For Apache 2.0, include NOTICE file contents if present

You may keep your patches proprietary if you choose. You may distribute patched binaries without providing source code. You may incorporate patched components into closed-source products. The permissive license continues to apply to the original code, but your modifications are yours to license as you see fit.

Copyleft License Patching

Copyleft licenses create more substantial obligations when you modify and distribute:

GPL v2/v3: If you distribute modified GPL software (binaries or source), you must: - Provide complete corresponding source code - License your modifications under GPL - Include license text and copyright notices - For GPLv3, provide installation information for user-installable devices

LGPL: Library linking without modification typically doesn't trigger copyleft. However: - If you modify the LGPL library itself, modifications must be LGPL-licensed - You must enable users to relink with modified library versions - Static linking may create additional obligations depending on interpretation

AGPL: Network interaction triggers source availability requirements: - Users interacting over a network must be able to obtain source - This includes your modifications (security patches) - SaaS deployments cannot avoid AGPL obligations through server-side use

MPL 2.0: File-level copyleft means: - Modified MPL files must remain MPL-licensed - New files you create may use different licenses - You must provide source for modified MPL files

Internal Use Exception

Most copyleft licenses trigger obligations upon "distribution" or "conveyance" to third parties. Internal use—running patched software on your own systems without distributing to others—generally doesn't trigger source availability requirements. This means:

  • Patching components for internal systems typically requires no source disclosure
  • Using patched libraries in internal tools doesn't create external obligations
  • The line between "internal" and "distribution" can blur in complex deployments

SaaS and cloud deployments complicate this analysis. Traditional GPL doesn't consider network access to be distribution—you can run modified GPL software as a service without triggering source requirements. AGPL explicitly addresses this, requiring source availability for network-accessible deployments.

Copyleft Compliance in Security Fixes

When security fixes require copyleft compliance, organizations must balance urgency with legal obligations.

Emergency Patching Scenarios

A critical vulnerability requires immediate patching. The vulnerable component is GPL-licensed. You must distribute patched software to production systems and possibly to customers. What are your obligations?

If you're distributing patched binaries: 1. You must offer source code access (written offer valid for three years, or source alongside binaries) 2. Your patches must be GPL-licensed 3. Complete corresponding source must be available, including build scripts and dependencies

This doesn't mean you must publish patches publicly. GPL requires source availability to recipients of binaries, not to the world. You may provide source through: - Physical media accompanying distribution - Written offer for source (GPLv2) with delivery mechanism - Network download access equivalent to binary access

Contributing Fixes Upstream

Security fixes should generally be contributed upstream when possible. This serves both security (broader fix deployment) and compliance (upstream distribution handles licensing). However, contributing security fixes creates timing considerations:

  • Embargo periods: Security researchers often coordinate disclosure timing; upstream contribution may conflict with embargo agreements
  • Responsible disclosure: Contributing before public disclosure may expose the vulnerability prematurely
  • Competitive concerns: Competitors using the same component benefit from your security investment

Organizations should establish processes for security contribution decisions, considering licensing obligations alongside disclosure coordination and business factors.

Contribution Agreements and Rights

Contributing security fixes to open source projects may require signing contribution agreements that affect your intellectual property rights.

Contributor License Agreements (CLAs)

Many projects require contributors to sign Contributor License Agreements (CLAs) before accepting contributions. CLAs typically:

  • Grant the project broad rights to use your contributions
  • Affirm you have the right to make the contribution
  • May grant patent licenses
  • May allow the project to relicense contributions

CLA terms vary significantly. Some grant exclusive rights; others grant non-exclusive licenses. Some include patent grants; others don't. Some allow relicensing to any future license; others restrict relicensing options.

Before signing CLAs on behalf of your organization, ensure: - Appropriate authority exists to sign (often requires legal or executive approval) - CLA terms are acceptable to your organization - Your organization actually owns the rights being granted (employee work-for-hire, etc.)

Developer Certificate of Origin (DCO)

Some projects use the Developer Certificate of Origin (DCO) instead of CLAs. The DCO is a lightweight attestation that:

  • You have the right to submit the contribution
  • You're submitting under the project's license
  • You understand contributions are public and recorded

DCO sign-off (typically Signed-off-by: lines in commits) represents a simpler commitment than CLAs. However, DCO doesn't grant additional rights beyond the project license—the project receives only the rights that license provides.

Security Fix Contribution Considerations

When contributing security fixes:

  1. Verify you have the right to contribute (work-for-hire, assignment agreements, etc.)
  2. Check whether the project requires CLA or DCO
  3. Obtain necessary organizational approvals before signing agreements
  4. Consider whether contribution timing aligns with disclosure coordination
  5. Document the contribution for license compliance tracking

Organizations should establish pre-authorization for routine security fix contributions, avoiding delays when critical patches need upstream submission.

License Compatibility in Dependency Trees

Modern software incorporates dozens to hundreds of dependencies, each with its own license. License compatibility—whether licenses permit combined distribution—affects your ability to deploy and distribute software containing security fixes.

Compatibility Challenges

License incompatibility arises when license terms conflict:

  • GPL and proprietary: GPL requires derivative works be GPL-licensed; proprietary licensing conflicts
  • GPLv2 and GPLv3: Some interpretations find GPLv2-only code incompatible with GPLv3
  • GPL and Apache 2.0: Apache 2.0 is GPLv3-compatible but GPLv2-incompatible due to patent termination clause differences
  • AGPL network requirements: May conflict with deployment models other components assume

Security Update Compatibility Impact

A security update that changes a component's dependencies may introduce license incompatibilities:

  • New dependency with incompatible license
  • Dependency upgrade changing license version (common with relicensing)
  • Transitive dependency changes affecting overall license profile

Before applying security updates affecting dependencies, verify: - New or changed dependencies and their licenses - Compatibility with existing license profile - Impact on distribution rights

Managing License Inventory

Effective license management requires:

  • Maintaining accurate license inventory (complement to SBOM)
  • Automated license detection in dependency analysis
  • License compatibility checking in CI/CD pipelines
  • Review processes for license changes

Tools supporting license compliance include:

Integrate license checking with security tooling. When vulnerability scanners identify component updates, verify license compatibility before deployment.

Commercial Use Restrictions

Some licenses include restrictions on commercial use or other limitations that may affect security activities.

Non-Commercial Licenses

Certain licenses—like Creative Commons Non-Commercial variants—restrict commercial use. Software under these licenses may not be appropriate for commercial products regardless of security status. Components with:

  • NC (Non-Commercial) restrictions
  • "Personal use only" limitations
  • Academic or research-only terms

should be identified and flagged during license inventory. Security patching doesn't override commercial use restrictions—you may fix vulnerabilities but still cannot use the result commercially.

Commons Clause and Similar Restrictions

The Commons Clause and similar license modifications add restrictions to otherwise open source licenses:

"The Software is provided to you by the Licensor under the License, as defined below, subject to the following condition: Without limiting other conditions in the License, the grant of rights under the License will not include, and the License does not grant to you, the right to Sell the Software."

Software with these restrictions isn't considered open source by Open Source Initiative definitions but appears in repositories alongside open source components. Your SBOM and license inventory should identify these restrictions to prevent compliance violations.

Source-Available vs. Open Source

Some projects use source-available licenses that permit viewing and modification but restrict distribution or commercial use:

  • Business Source License (BSL)
  • Server Side Public License (SSPL)
  • Elastic License 2.0
  • Various proprietary licenses with source access

These licenses may permit security patching for internal use while restricting distribution of patched versions. Understand the specific terms before assuming open source-like freedoms.

When to Consult Counsel

Certain situations warrant legal consultation beyond general guidance:

  • Unclear license terms: Ambiguous language requiring interpretation
  • Novel distribution models: Cloud, SaaS, API access affecting license applicability
  • CLA signing authority: Organization-binding agreements requiring authorization
  • License violations discovered: Potential compliance failures requiring remediation
  • Acquisition due diligence: Evaluating license obligations in M&A contexts
  • Commercial use questions: Business model changes affecting license applicability
  • Contribution strategy: Establishing contribution policies and agreements

Establish relationships with counsel familiar with open source licensing before urgent situations arise. Legal review during security emergencies creates unacceptable delays; pre-established policies and pre-authorized procedures enable rapid response.

Recommendations

We recommend organizations integrating licensing with security processes:

  1. Maintain license inventory alongside SBOM, tracking all component licenses and restrictions

  2. Integrate license checking into CI/CD pipelines, flagging incompatibilities before deployment

  3. Establish contribution policies pre-authorizing security fix contributions under defined conditions

  4. Pre-negotiate CLA signing authority enabling rapid upstream contribution when needed

  5. Document copyleft compliance procedures ensuring source availability when distributing patched copyleft software

  6. Train security teams on basic licensing implications, enabling informed initial triage

  7. Establish legal relationships before emergencies, with counsel familiar with open source licensing

  8. Review licenses during security updates verifying compatibility when dependencies change

The intersection of licensing and security requires coordination between legal, security, and development teams. Organizations that integrate these disciplines respond more effectively to security issues while maintaining compliance.