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.
Not sure whether this implementation will be lighter on resources than what Lemmy currently uses. Given the overhead of the JVM though, it’s unlikely it will be supported by, say, a single Raspberry Pi
JVM doesn’t have much overhead. Java 1.3 days are long gone.