> Therein lies the problem. When dealing with the law, you don't want to be relatively sure that you won't go to prison or won't get sued for $1M, you want to be completely sure.
Not really. Unless you are redistributing it does not affect you at all.
> Something like the GPL is complex and non-standard as far as its interactions with the legal system go
it is widely used, and most people are running some copyleft software anyway, most commonly GPL or a variant such as LGPL. Linux servers, Android phones, routers, web browsers....
Therein lies the problem. When dealing with the law, you don't want to be relatively sure that you won't go to prison or won't get sued for $1M, you want to be completely sure.
Something like the GPL is complex and non-standard as far as its interactions with the legal system go, because it is essentially a sort of hack of copyright law. If it goes before a court, you have no idea what might potentially happen. So rather than deal with that kind of complexity and uncertainty, you'd use something under MIT or Apache License that is just much better understood.