HEIC conversion uses heic-to 1.6.6 by Hopper Gee, under LGPL-3.0-or-later.
The decoder is distributed unmodified and separately from DHEBE application code.
Its license does not replace the license of unrelated DHEBE source files.

The complete upstream license and README are served alongside the module:
/heic/LICENSE.txt
/heic/README.txt
/third-party/GPL-3.0.txt (GNU GPL incorporated by the LGPL)

Replaceable module: /heic/heic-to-1.6.6.js
Integration source: /heic-converter.worker.js
You may replace the decoder with a compatible modified version. The integration
is a separate ES module, not a restriction on modifying or debugging the library.

Exact upstream source revision for package 1.6.6:
https://github.com/hoppergee/heic-to/tree/4045b8d7607e326c2b479cc424c7a60519b42dae
Source archive:
https://github.com/hoppergee/heic-to/archive/4045b8d7607e326c2b479cc424c7a60519b42dae.tar.gz
Published package:
https://registry.npmjs.org/heic-to/-/heic-to-1.6.6.tgz

Upstream build instructions and dependency notices are in the corresponding source.
The embedded decoder is based on libheif 1.23.6:
https://github.com/strukturag/libheif/tree/v1.23.6
https://github.com/strukturag/libheif/blob/v1.23.6/COPYING
Follow the applicable licenses for modifications and redistribution.