It's so easy to overlook the importance of tooling around a language, unlike (say) syntax.
Are there any languages that explicitly put tooling first? Maybe Kotlin or Pharo?
I'm a huge fan of languages that require you to explicitly export your functions (e.g. pub in Rust or export in JS).
It's much easier to change than a separate header file (.h in C, .mli in OCaml) and it enables local reasoning. You can see from the definition if it's exported.
Are there any FOSS licensees that explicitly allow people to train AI models on the source code?
This seems like a useful addition, and there's already precedent with the "classpath exception" for the GPL.
