Honestly, if a project is so blinded by zealotry that even a non-copyleft license like Apache 2.0 isn't free enough, then I don't see any reason to engage with them in any form.
"In addition, the clause about the patent license is problematic because a patent license cannot be granted under Copyright law, but only under contract law, which drags the whole license into the domain of contract law. But while Copyright law is somewhat standardized by international agreements, contract law differs wildly among jurisdictions. So what the license means in different jurisdictions may vary and is hard to predict."
From what I recall, Apache httpd 2.0 came out a long time before Apache License 2.0. A quick check of Wikipedia confirms it:
> The Apache HTTP Server codebase was relicensed to the Apache 2.0 License (from the previous 1.1 license) in January 2004, and Apache HTTP Server 1.3.31 and 2.0.49 were the first releases using the new license.
If OpenBSD wanted to use httpd 2.x without switching to the new license, they could have forked 2.0.48. Their reasons for not using httpd 2.x were entirely technical. Architecturally, 2.x was a major departure from 1.x, and the OpenBSD developers were grognards who rejected it because they weren't interested in a web server that deviates from tradition. And since Apache still maintained 1.3.x for ages after 2.0 came out, it made their decision easier (well, until the license change hit).
And this is a huge digression anyway: I honestly don't see a reason to cater to a group of people who would cut off their nose to spite their face. The LLVM team has better things to do with their time.
nginx was initially considered, but the upstream wasn't receptive to patches that OpenBSD worked on, including a chroot(2) support and security patches, i.e: reallocarray to protect against arithmetic overflows. At the time, Nginx cared more about it's Nginx PLUS offering and less about the community.
That doesn't seem like a fair description of what happened. I think it was more that the OpenBSD project didn't want Apache 2.x in the base system, and thought that if people wanted it they could get it from the package manager. There might also have been some licensing issues in the sense that they'd prefer no Apache license at all, but that was apparently secondary to the changes in Apache code that contributed to the decision.
It also comes with some weird bookkeeping issues, like having to mark changed files in ambiguous circumstances, and requirements for how a file with a particular name (NOTICE) must legally be treated. These kinds of things can add to the burdens involved in building derived works, maintaining modified forks, or borrowing code.