The licensing model¶

Media tooling licensing is where most projects get vague. ffmpeg-wasi keeps three licences deliberately distinct, so you always know exactly what you're holding.

Three licences, kept apart¶

1. This repository's source — MIT¶

The build tooling (build/) and the engine (src/driver.c) are MIT. Two facts keep it that way:

• It vendors no FFmpeg source. FFmpeg (and any GPL dependency such as x264) is cloned at build time, never committed here.
• It links nothing. The tooling orchestrates a build — clone, configure, compile, package. It is not a derivative work of anything GPL, so it stays MIT, and it is yours to reuse.

That MIT pipeline — the reference "FFmpeg → WASI, libav-direct" build — is the valuable, reusable part we own.

2. The released artifacts — LGPL or GPL (your choice)¶

FFmpeg's libraries are LGPL-2.1-or-later by default. The artifact's licence is set entirely by what we enable:

LGPL is the floor. We cannot relicense libav* below it — it's the FFmpeg project's code, not ours. But LGPL is proprietary-compatible (you may use it in closed software, subject to its relink provision), which is what matters for adoption.

3. Your code that consumes the artifact — unaffected¶

afmpeg, or whatever loads the module, just downloads a .wasm. The LGPL/GPL obligation attaches to that artifact and whoever distributes it — never to the consuming source. afmpeg stays permissive throughout.

Why shipping both variants is clean¶

Every release publishes both ffmpeg-wasi-lgpl.wasm and ffmpeg-wasi-gpl.wasm, so you pick the licence that fits and never have to build. Distributing two separate, independent artifacts together is mere aggregation (GPLv3 §5): the GPL artifact does not "infect" the LGPL artifact, the MIT tooling, or your code. They simply coexist.

Obligations we meet¶

• Per-asset labelling — each artifact states its licence; the provenance manifest records variant + licence.
• Corresponding source — for every released binary, the source is the pinned upstream FFmpeg/x264 plus this public repository (our scripts + engine). Anyone can rebuild.
• LGPL relink — because the build is public and the FFmpeg version pinned, a user can relink the LGPL artifact against a modified libav*.

In one sentence¶

MIT is what we own; LGPL is the floor for the artifact; GPL is opt-in for libx264; and your code stays yours.