So. Homebrew is illegal now too, then?
EDIT: People seem to be misunderstanding this screenshot. This is me running a program installed by Brew and it being blocked by macOS Gatekeeper. You can see me executing it from the command line and you can see in the error message that Homebrew downloaded it. Although brew is in general working for me, this particular formula's app got blocked. After making the post I resolved the problem and do not need help.
@anderson_jon From memory: After dismissing the "cannot be opened" box I was able to find a log of events in Settings, I think the Privacy & Security box. When I selected the denial of gtkwave, it allowed me to manually approve gtkwave.
The way I would have normally handled this was by, instead of double-clicking the app, right-clicking it and selecting "open", which for some unfathomable reason is the backdoor to the "sure you want to open?" box. But this event happened command line.
mcc
Jon Anderson