Some open source projects use the Apache 2.0 license “with LLVM Exception” SPDX: "Apache-2.0 WITH LLVM-exception"). So what is the “LLVM exception” exactly, and why do some projects add it to their license?

The question often comes up of how Snaps and Flatpaks influence copyleft, GPL and LGPL licenses. It is a common misconception that these new packaging formats significantly influence license compliance.

When I submitted my first paper, I realized I had no idea who owned my research! Was I authorized to transfer the rights to a journal or did I need someone else’s permission? After some digging, I found the answer and wrote it all up in a neat little document. So here’s the dusted off version, in case it’s useful to anyone else.