Many licenses haven't been tried in court, including the AGPL, yet it's used fairly broadly.
Corporations vastly prefer BSD/MIT style licenses or at most GPLv2.
GPLv3 is avoided, AGPL is avoided even more.
Likewise for GPLv3 and Tivoized corporations.
That is the context from which I'm speaking, where enforcing openness through legal means is not a concern as the license is permissive (I imagine you were thinking of protecting GPL software, which is kind of the opposite situation). There have been zero court cases involving legal dispute over MIT licensed software.
The question is, how do I know that a contributor to software under the JSLint license (perhaps a corporation that paid an employee to contribute something) won't sue me on the grounds that I'm doing evil with their code?
That isn't true at all. If someone takes GCC, makes some changes and re-releases GCCv2 as closed source, there's no open source boogeyman that will force GCCv2 developers to release their code. It's up to courts, and by extension lawyers. Free software implicitly depends on lawyers to hold up the contract of Free Software.
If lawyers tell you "this contract is unusable because of this clause" then you don't have free software, you have a weird proprietary license. The entire point of free software licenses is to define rules for lawyers to play "their games in court". It's worthless otherwise.