Earlier quoted context omitted.
Homebrew Project Leader here. Yes, this only affects casks, not formulae, whether formulae are built from source or use Homebrew's bottles (binary packages) or bottles from taps.
As an open-source developer, is there a way to have my apps pass Gatekeeper without paying the $100/year Apple ransom and notarizing them? I think it’s the crux of the problem. As I’m writing these lines, Homebrew has 7656 casks in the official cask tap[1]. I’m not sure exactly how many of those are unsigned but if we assume 4000 then signing them all would be an additional $400,000/year extorted by Apple from the op…
Users will need to `brew install myorg/mytap/appname` instead of just `brew install appname`, but I think that's the only real option at this point.