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.
Lemmy doesn’t have to have missing features for someone to want to write their own implementation. And in a decentralized system you want multiple implementations to exist. This is a good thing