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.
Well there’s still the question of using MySQL (?) rather than postgresql, where all manner of expertise about the DB can be useful to share. Not sure what kbin uses, but pgsql is pretty common around the fediverse.
And yea, it is all ActivityPub. I’m just not as faithful in that as others tend to be. It seems to be a fuzzy system that allows idiosyncrasies to creep in. Mastodon and Lemmy don’t get along too well and so sometimes AP just isn’t enough (I’ve just been trying to help someone whose masto instance seems not able to post to lemmy). At this moment, getting along is valuable for the platforms, for the fediverse and for us users.