FOSS-chain: Blockchain OSS Compliance

• FOSS-chain Platform is a web-based system that integrates blockchain technology with smart contracts to enforce automated open source license compliance.
• It leverages function-level SHA-256 hashing and a pre-computed license compatibility matrix to detect code reuse and prevent incompatible licensing.
• The platform enhances transparency and accountability in OSS development, with promising user study feedback despite scalability and language support challenges.

The FOSS-chain Platform is a web-based system integrating blockchain technology to automate and enforce open source software (OSS) license compliance throughout the development and distribution lifecycle. Addressing the multifaceted challenges posed by complex licensing obligations and frequent code reuse across heterogeneous projects, the platform leverages immutable smart contract records and code-level provenance analysis to perform compliance checks, record software transactions, and facilitate compatibility assessment for derivative works. This architecture is designed to enhance the transparency, accountability, and legal certainty of OSS re-use in ecosystem-scale software engineering environments (Iacovou et al., 2 Oct 2025).

1. Blockchain-Backed License Compliance Mechanisms

At the core of the FOSS-chain Platform is the deployment of smart contracts on the Ethereum blockchain to automate and record licensing actions. Two contract types constitute the principal compliance workflow:

• DownloadAgreement Contract: When software is downloaded, this contract records the user's wallet address, software project identifier, license type, and timestamp as a blockchain event. This provides evidence of explicit agreement to the license at each point of acquisition.
• LicenseManager Contract: During software uploads (e.g., for new projects or derivative works), code function boundaries are detected and each function is hashed (using SHA-256). These hashes are matched against hashes of known projects previously registered on the blockchain. If matches are detected, indicating code reuse, the contract retrieves the associated upstream license(s) and assesses compatibility with the newly declared license.

Uploads failing the compatibility check—such as attempts to relicense copyleft-licensed code with a non-permissive license—are automatically rejected by the platform, thereby proactively enforcing combinatorial license constraints and precluding inadvertent or willful violations (Iacovou et al., 2 Oct 2025).

2. Technical Implementation and Formalization

The platform architecture embodies several key technical elements:

Function-Level Hashing and Provenance

Each code function $f$ is processed as follows: $H(f) = \text{SHA256}(\text{code}(f))$ These hashes serve as provenance tags: if a new upload contains a function $f'$ with $H(f') = H(f)$ for a previously registered $f$, code provenance is inferred regardless of packaging or repository boundaries.

License Compatibility Matrix

A pre-computed license compatibility matrix $\mathcal{C}$ specifies for each OSS license $L_1$ the set of licenses $\mathcal{C}(L_1)$ with which code under $L_1$ may be relicensed. At upload: $$\text{if } L_2 \in \mathcal{C}(L_1) \text{, allow upload; else, block.}$$ This directly implements upstream compatibility constraints (e.g., forbidding relicensing GPL code under MIT, but permitting MIT code within GPL projects).

Blockchain Transaction Structure

Every licensing-relevant action triggers the creation of a blockchain record: $$\text{Block}_i = \{\text{prevHash}_{i-1}, \text{Tx}_i, \text{timestamp}_i\}$$ where $\text{Tx}_i$ encodes all compliance metadata: project, user wallet, license, hashes, etc. The chained hash structure provides tamper-resistance and provenance for compliance events.

3. Evaluation and User Study

An empirical evaluation was conducted using a convenience sample of 34 participants (academic and industry), including 73.5% with a software engineering background (Iacovou et al., 2 Oct 2025). The evaluation employed a structured questionnaire following tool demonstration.

Key findings:

• 85.3% of users routinely use OSS, though only 32.4% had expertise in OSS licensing.
• Major concerns cited were lack of license awareness and absence of concrete enforcement in current practice.
• Despite modest understanding of blockchain, 67.6% agreed that blockchain-integrated compliance is promising.
• Usability feedback was positive on general function and understandability, but pointed to specific improvement needs (notably navigation and transparency in code derivation detection).

Non-parametric (Kruskal-Wallis H) analysis did not find statistically significant variation in reception based on technical background or license familiarity, suggesting general broad utility.

4. Supported Licenses and Compliance Enforcement

The FOSS-chain prototype supports 14 widely utilized OSS licenses (including MIT, Apache-2.0, GPL, LGPL, MPL, AGPL) (Iacovou et al., 2 Oct 2025). Enforcement is determined via:

• Compatibility Matrix: Encodes all pairwise license constraints based on established legal analyses.
• Upload Process: If a new artifact contains code previously registered under a different license, the declared license is checked against all relevant upstream licenses for compatibility.
• Copyleft: Any attempt to relicense derivative works of copyleft code under an incompatible permissive license is algorithmically blocked.

5. Implementation Limitations and Future Challenges

Known limitations in the current design include:

• Imperfect Similarity Detection: Function-level SHA-256 hashes are sensitive to minor syntactic changes (e.g., variable renaming), possibly missing some forms of derivative works or producing false negatives. Future directions include AST-based structural analysis or machine learning models for code similarity.
• Language Support: Present support is limited to C, Java, and Python based on regular expression-based function detection. Plans exist to expand coverage to more languages (JavaScript, C++, C#, etc.).
• Wallet Management: Initial user wallet registration is manual, presenting scalability and security obstacles. Integration with automated wallet generation and decentralized identity management is anticipated.
• Blockchain Scaling: Use of Ethereum is feasible for small deployments but may incur significant costs and delays at larger scale due to gas fees and transaction throughput.

6. Practical Implications and Significance

FOSS-chain represents a shift from ex post compliance auditing to proactive, transaction-level enforcement for OSS license management. Tangible impacts include:

• Immediate compliance feedback at point of derivative work upload, reducing inadvertent license violations and subsequent legal/extralegal risk.
• Enhanced transparency and traceability of OSS provenance throughout its lifecycle, beneficial to organizations with regulatory compliance requirements or large dependency trees.
• Greater reliability for small teams and enterprises lacking specialized legal resources, provided through consistent, automated compliance checking.

A plausible implication is that, as the platform provenance and compatibility analysis matures (especially with improvements in code similarity detection and broader language coverage), FOSS-chain may serve as a foundational infrastructure component for compliance-by-design workflows in large-scale, multi-party OSS development (Iacovou et al., 2 Oct 2025).

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In summary, the FOSS-chain Platform operationalizes OSS license governance by combining blockchain-based immutable logging, code-level provenance via cryptographic hashing, and a rule-based compatibility matrix, addressing critical needs for automation, transparency, and enforcement in distributed open source ecosystems. Preliminary user paper results indicate promising acceptance and impact potential for technical audiences, though further work is required for scaling, robustness, and expanded language support.