Licence

Every dataset served here is a work of the United States Government and is public domain.

The short version. Take it. Use it commercially. Redistribute it. You owe nothing — no share-alike, no non-commercial restriction, and no attribution obligation anywhere in the critical path. That is not generosity; it is a property of the sources, and it was a selection criterion.

The data

Source	What it gives	Licence	Key?
USITC Harmonized Tariff Schedule	Duty rates, units, footnotes, programme letters, chapter 99	Public domain (17 U.S.C. 105)	none
Office of the Federal Register	Tariff proclamations, rules and notices	Public domain (17 U.S.C. 105)	none
U.S. Census Bureau, Schedule C	Country and territory codes with ISO alpha-2	Public domain (17 U.S.C. 105)	none
eCFR, Title 19	Customs regulation citations	Public domain (17 U.S.C. 105)	none

The one notice that is required

The Census Bureau's API terms of service ask that any product using them display this, and it is a condition of using the API rather than a condition on the data:

This product uses the Census Bureau Data API but is not endorsed
or certified by the Census Bureau.

It travels in every response that carries Census-derived data, and in meta.json. Keep it if you redistribute those records.

What was excluded, and why

Several obvious sources are missing on purpose. The reasoning is served live at /v1/sources so it cannot rot in a document nobody reads.

Source	Why not
Census international trade API	Would have given import volumes, values and the duty actually collected — the most interesting data in this domain. It requires an API key, and this service is built to need none from anyone. This is the biggest gap and it is declared, not hidden.
FAOSTAT	CC BY 4.0 — an attribution obligation rather than public domain — plus FAO terms forbidding use “in conjunction with the promotion of a commercial enterprise”. Fails the public-domain bar this service holds itself to.
OIV	Terms forbid “any other use than those specified above, including commercial use”. A hard blocker.
UN Comtrade	The keyless preview works once and then rate-limits for the hour; the full API needs a subscription key, and UN terms are not an open licence.
Eurostat Comext	Reuse carries a source-acknowledgement obligation under Decision 2011/833/EU.
USITC DataWeb	Free, but behind an account. A registration is still a registration.

The code

MIT. The server, the parser and the build are all in the repository; if a plan's limits are in your way, run your own copy rather than buying one.

Derived fields

Some fields are computed by this service rather than published by USITC — the full description path, the parsed rate terms, the programme names, and every duty estimate. Each is marked in the response (derived, estimate), and the raw published string is always served alongside so you can check the working. Those derivations are MIT along with the rest of the code; the underlying facts remain public domain.