[sneak]

Reverse engineering publicly available proprietary software distributed as freeware to reimplement free software replacements is not illegal.

[tbodt]

Can you help convince me of this?

Also I'd encourage you to contact the owners of the repositories listed in Google's DMCA notice against the Widevine cryptographic key and help them file a counter-notice. https://github.com/github/dmca/blob/master/2020/11/2020-11-0...