Seems like an interesting effort. A developer is building an alternative Java-based backend to Lemmy’s Rust-based one, with the goal of building in a handful of different features. The dev is looking at using this compatibility to migrate their instance over to the new platform, while allowing the community to use their apps of choice.
I am not writing it off, I am saying it has no competition in the browser… therefore irrelevant to the discussion at hand.
and btw, even in the link https://madnight.github.io/githut/#/pull_requests/2023/4 Javascript is not first, Python is, over Java.
but once again, you would actually have to look for the backed JS applications, you are not choosing java over JS for the web, at best you would choose JSF and that still uses javascript.