To answer the second part of your question, if you modify code released under GPL, you need a way to provide a machine-readable copy of your modifications to your users.
So, it doesn't need to be publicly available (as in, you and me are not Onyx users, therefore we don't need to have access to it), just to its users. Screenshot shows their user requesting it and being denied the request, hence, GPL violation.
Indeed - I amended the show waves filter in ffmpeg to create square wave forms for, but my C is terrible and I’m far too embarrassed to commit to a public code forum. As the binary goes no further than my own machines there’s no issue.
So, it doesn't need to be publicly available (as in, you and me are not Onyx users, therefore we don't need to have access to it), just to its users. Screenshot shows their user requesting it and being denied the request, hence, GPL violation.
https://www.gnu.org/licenses/gpl-faq.en.html#GPLRequireSourc...