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License

Type-safe SPDX license identifiers for smart contract metadata.

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Overview

Branded string type representing SPDX license identifiers. Used in Solidity source files and smart contract metadata to identify licensing terms. Includes validation for OSI-approved licenses.

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Quick Start

import * as License from '@tevm/voltaire/License'

// Create license identifier
const mit = License.from("MIT")
const apache = License.from("Apache-2.0")
const unlicensed = License.from("UNLICENSED")

// Convert to string
License.toString(mit)  // "MIT"

// Check OSI approval
License.isOSI("MIT")        // true
License.isOSI("Apache-2.0") // true
License.isOSI("UNLICENSED") // false

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Common Licenses

LicenseOSI ApprovedDescription
MITYesPermissive, minimal restrictions
Apache-2.0YesPermissive with patent grant
GPL-3.0YesStrong copyleft
GPL-2.0YesStrong copyleft (earlier version)
LGPL-3.0YesWeak copyleft for libraries
BSD-3-ClauseYesPermissive with attribution
BSD-2-ClauseYesSimplified BSD
ISCYesSimplified BSD-like
MPL-2.0YesWeak copyleft file-level
AGPL-3.0YesStrong copyleft + network use
UNLICENSEDNoProprietary/no license

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API Reference

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Constructors

import * as License from '@tevm/voltaire/License'

// Create from SPDX identifier
const license = License.from("MIT")

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Methods

import * as License from '@tevm/voltaire/License'

const license = License.from("Apache-2.0")

// Convert to string
License.toString(license)  // "Apache-2.0"

// Check if OSI-approved
License.isOSI(license)     // true
License.isOSI("GPL-3.0")   // true
License.isOSI("UNLICENSED") // false

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Constants

import { COMMON_LICENSES, OSI_APPROVED_LICENSES } from '@tevm/voltaire/License'

// Common SPDX license identifiers
COMMON_LICENSES: string[]

// OSI-approved open source licenses
OSI_APPROVED_LICENSES: string[]

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Solidity License Identifier

SPDX license identifiers are required in Solidity files since version 0.6.8: 
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
The identifier appears in compiled contract metadata and can be used to:
  • Identify licensing terms programmatically
  • Filter contracts by license type
  • Ensure compliance with open source requirements

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Use Cases

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Contract Metadata Analysis

import * as License from '@tevm/voltaire/License'

interface ContractMetadata {
  license: string
  compiler: string
  source: string
}

function analyzeContract(metadata: ContractMetadata) {
  const license = License.from(metadata.license)

  return {
    license: License.toString(license),
    isOpenSource: License.isOSI(license),
    isPermissive: ["MIT", "Apache-2.0", "BSD-3-Clause"].includes(
      License.toString(license)
    )
  }
}

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License Filtering

import * as License from '@tevm/voltaire/License'
import { OSI_APPROVED_LICENSES } from '@tevm/voltaire/License'

interface Contract {
  address: string
  license: string
}

function filterOpenSourceContracts(contracts: Contract[]): Contract[] {
  return contracts.filter(c => License.isOSI(c.license))
}

function filterByLicense(contracts: Contract[], allowed: string[]): Contract[] {
  return contracts.filter(c => allowed.includes(c.license))
}

// Only permissive licenses
const permissive = filterByLicense(contracts, ["MIT", "Apache-2.0", "BSD-3-Clause"])

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References