Iskra distributes an unmodified buildLibheif JavaScript module from:
heic-to 1.6.5, src/lib/libheif-without-unsafe-eval.js (renamed libheif.mjs).
Build header: libheif 1.23.5, USE_UNSAFE_EVAL=0, LIBDE265_VERSION=1.0.16.
Licenses: LGPL-3.0-or-later; copyright notices are preserved in the source archives.
The Iskra application communicates with this separately loaded module through a Worker.
You may replace this module with a modified compatible build; the application does not prohibit reverse engineering for debugging modifications to the library.

Corresponding source and build instructions are provided next to this notice:
source/heic-to-1.6.5.tgz (wrapper source, original generated module, esbuild.mjs, README.md)
source/libheif-1.23.5.tar.gz (library source, licenses, build-emscripten.sh)
source/libde265-1.0.16.tar.gz (HEVC decoder source and licenses)

Upstream build recipe from heic-to README.md:
Build libheif using Emscripten and build-emscripten.sh, with
LIBDE265_VERSION=1.0.16 USE_UNSAFE_EVAL=0 USE_WASM=0.
The README documents its llvm-nm path adjustment for macOS.
For a replacement, export the compatible default buildLibheif factory as libheif.mjs.
No changes have been made to the upstream decoder file.