Thank you for pointing this out, to be completely honest, I did not consider licensing because the website started as a collection of tools I built to run locally and get into video/audio codecs then I realised it is already a decent collection of tools that other people might want to use too. But I will be making the needed changes to comply fully tonight. At least I comply with this: `Do not misspell FFmpeg (two capitals F and lowercase "mpeg")` I realised I have some more reading to do regarding GPL vs LGPL because of the wasm project.
Any reason not to just open source it? Personally I'd love to hack on it :-) IANAL, but IMHO AGPL would be a good fit here as it complies with LGPL and also ensures nobody besides you (the copyright holder) can stand it up for profit without contributing back).
You should look into how other companies and tools that use FFMPEG handle this situation.
I wonder if you can keep your application itself closed source, but make an open-source adapter that handles the interaction with FFMPEG.
I'm not super familiar with open source licensing, and IANAL, so make sure to do your own research :)
As an example, I believe Audacity required me to install ffmpeg manually myself, and add it to my path. This is slightly different since Audacity itself is also open source. But could be helpful to reference.