[@TK] You make a very valid point — and it looks like the developer actually listened. I just checked the latest version (v1.0.55, released today) and they’ve switched the bundled FFmpeg builds from GPL to LGPL-compiled variants. The builds now come from BtbN/FFmpeg-Builds with the –enable-lgpl flag, and the installer includes both the full LGPLv3 license text and an updated THIRD_PARTY_LICENSES.txt that documents the LGPL compliance.
So it seems like the issue you raised has been addressed — the closed-source distribution now ships with LGPL FFmpeg binaries, which is the correct approach for a proprietary product. Good catch on the original GPL issue though, that was a legitimate concern.