libheif-js 1.19.8 (LGPL-3.0)
Upstream: https://github.com/catdad-experiments/libheif-js
libheif:  https://github.com/strukturag/libheif

Shipped UNMODIFIED as separate files (libheif.js + libheif.wasm) and loaded dynamically at runtime,
so this library can be replaced with your own build without rebuilding the rest of Petrel. That is
the relinking right the LGPL exists to protect.

LICENCE TEXTS, BOTH REQUIRED:
  LICENSE  - GNU Lesser General Public License v3. This is a SUPPLEMENT, not a standalone licence:
             its own text says it "incorporates the terms and conditions of version 3 of the GNU
             General Public License, supplemented by the additional permissions listed below".
  COPYING  - GNU General Public License v3, the licence the LGPL builds on. LGPL-3.0 section 4(b)
             asks that both be supplied, which is why COPYING sits here too.

Only libheif is covered by these licences. The rest of Petrel is not.