Browser GIF export uses @ffmpeg/ffmpeg 0.12.15 (MIT) and the unmodified single-thread @ffmpeg/core 0.12.10 build (GPL-2.0-or-later, with its codec licenses). The WASM is distributed gzip-compressed without changes. No FFmpeg executes on the server.
Project source, license texts and build scripts: https://github.com/ffmpegwasm/ffmpeg.wasm
Pinned npm distribution: https://www.npmjs.com/package/@ffmpeg/core/v/0.12.10
GPL-2.0 text: /gif-export/COPYING.GPL-2.0.txt
FFmpeg source: https://github.com/FFmpeg/FFmpeg ; upstream component/build versions: https://github.com/ffmpegwasm/ffmpeg.wasm/tree/main/build
FFmpeg legal information: https://ffmpeg.org/legal.html