ZoneBuilder uses LAME for browser MP3 encoding, including durable Workbench and Practice recording saves. The local worker loads the encoder on demand.
| Component | Version | License | Distributed form |
|---|---|---|---|
| LAME MP3 Encoder | 3.100, commit 98db548e8e851defbba3184125ce10725355c332 |
GNU Library General Public License v2.0 or later | Encoder library statically linked into mp3.wasm; matching source download |
| wasm-media-encoders | 0.7.0, commit 4a45333baadbab312d1cc0911151dfad23157c51 |
MIT | C bridge inside WASM; separate JavaScript wrapper; matching source/build inputs |
LAME is used under the GNU Library GPL; its use is covered by that license. Read the full Library GPL v2.0 text. The source headers permit v2 or later. Do not substitute LGPL-2.1 wording for this license. LAME project: https://lame.sourceforge.io/.
Attributions from the encoding-engine source include Copyright (c) 1999–2000 Mark Taylor, 2000–2005 Takehiro Tominaga, 2000–2017 Robert Hegemann, 2000–2005 Gabriel Bouvigne, and 2000–2004 Alexander Leidinger. Other contributors’ original copyright/author notices are preserved in the retained source files. The wrapper/bridge is Copyright (c) 2020–2024 arseneyr: MIT license and warranty disclaimer. LAME’s original commercial-use notes are retained; the actual COPYING license governs the source/relink conditions.
Download the source/build package from this same application deployment, or use System → About → Third-Party Software → Download MP3 source. No login or request to the developer is needed. See download/build instructions, the SHA-256 manifest, and build provenance.
The package supplies the exact retained LAME source, the C bridge that links
against it, missing header/export graph and build/version inputs, original
licenses, and a documented MP3-only rebuild helper. The helper is separately
identified first-party build tooling. Upstream LAME/bridge source and the
published JavaScript wrapper are unchanged. The current WASM is built by
ZoneBuilder from this exact source package, using the documented recipe;
its SHA-256 is a1d8ba08c80ec5e63d62ad30685e9656c9032126e9cd3b9c95991f8e17083b68.
The archived published WASM is explicitly a historical comparison reference.
You may modify the encoder work for your own use and reverse engineer it for debugging those modifications, as required by Library GPL section 6. Build and replace the standalone WASM using the included instructions. Providing the linked bridge in source form supports that relinking; no proprietary bridge object is withheld. This notice does not assign a license to unrelated app code.
Materials are offered with equivalent download access alongside the binary under sections 4 and 6(c), rather than the alternative section 6(b) written offer. Distributors must retain matching materials and notices for each encoder binary they make available. The download is outside application startup and is not precached. An explicit download can be cached by the existing service worker.
The source package also retains distinct notices for source-only mpglib/hip (Library GPL v2-or-later), TinyXML (zlib-style), GNU build helpers (their GPL terms and distribution exceptions), and compiler/runtime support where noted. They are not additional automatically loaded application modules.