I really don't want to be that guy, but... Vanilla JavaScript already exists as a popular term for JavaScript without any framework. No jQuery, no React - just JavaScript. Calling a library VanJS (as short for "Vanilla JavaScript") is just going to cause confusion.
The repo's own description uses the phrase vanilla JavaScript in this way, and even mixes both meanings within a single sentence.
If the author likes the theme, I'm sure they can still use it indirectly. eg. "icecream.js: add a scoop of vanilla to your project". Or "Go nuts and sprinkle in some Reactive syntax". It's still very punnable, I assure you.
The repo's own description uses the phrase vanilla JavaScript in this way, and even mixes both meanings within a single sentence.
If the author likes the theme, I'm sure they can still use it indirectly. eg. "icecream.js: add a scoop of vanilla to your project". Or "Go nuts and sprinkle in some Reactive syntax". It's still very punnable, I assure you.