validate-npm-package-license

Give me a string and I'll tell you if it's a valid npm package license string.

var valid = require('validate-npm-package-license');

SPDX license identifiers are valid license strings:

var assert = require('assert');
var validSPDXExpression = {
validForNewPackages: true,
validForOldPackages: true,
spdx: true
};
assert.deepEqual(valid('MIT'), validSPDXExpression);
assert.deepEqual(valid('BSD-2-Clause'), validSPDXExpression);
assert.deepEqual(valid('Apache-2.0'), validSPDXExpression);
assert.deepEqual(valid('ISC'), validSPDXExpression);

The function will return a warning and suggestion for nearly-correct license identifiers:

assert.deepEqual(
valid('Apache 2.0'),
{
validForOldPackages: false,
validForNewPackages: false,
warnings: [
'license should be ' +
'a valid SPDX license expression (without "LicenseRef"), ' +
'"UNLICENSED", or ' +
'"SEE LICENSE IN <filename>"',
'license is similar to the valid expression "Apache-2.0"'
]
}
);

SPDX expressions are valid, too ...

// Simple SPDX license expression for dual licensing
assert.deepEqual(
valid('(GPL-3.0-only OR BSD-2-Clause)'),
validSPDXExpression
);

... except if they contain `LicenseRef`:

var warningAboutLicenseRef = {
validForOldPackages: false,
validForNewPackages: false,
spdx: true,
warnings: [
'license should be ' +
'a valid SPDX license expression (without "LicenseRef"), ' +
'"UNLICENSED", or ' +
'"SEE LICENSE IN <filename>"',
]
};
assert.deepEqual(
valid('LicenseRef-Made-Up'),
warningAboutLicenseRef
);
assert.deepEqual(
valid('(MIT OR LicenseRef-Made-Up)'),
warningAboutLicenseRef
);

If you can't describe your licensing terms with standardized SPDX identifiers, put the terms in a file in the package and point users there:

assert.deepEqual(
valid('SEE LICENSE IN LICENSE.txt'),
{
validForNewPackages: true,
validForOldPackages: true,
inFile: 'LICENSE.txt'
}
);
assert.deepEqual(
valid('SEE LICENSE IN license.md'),
{
validForNewPackages: true,
validForOldPackages: true,
inFile: 'license.md'
}
);

If there aren't any licensing terms, use `UNLICENSED`:

var unlicensed = {
validForNewPackages: true,
validForOldPackages: true,
unlicensed: true
};
assert.deepEqual(valid('UNLICENSED'), unlicensed);
assert.deepEqual(valid('UNLICENCED'), unlicensed);