Kbin is dead. Hopefully Ernst is himself not physically dead, but has stopped contributing. It was quite the fiasco as Kbin.social had to be defederated from since it was sitting un-administered and thus being used to spread spam across the entire Threadiverse.

Kbin's fork Mbin is still going strong, though with fewer users as time passes. There is even an app for it now: Interstellar.

It serves a very niche area though, where you want to interact with both the microblogging style Mastodon on the Fediverse and also Lemmy+PieFed on the Threadiverse (with newer additions being added e.g. nodeBB and flarum) using the same account rather than dedicated ones for each platform. Personally I feel like the UI is too geared towards the former and ignores what is much more commonly observed in the letter. Plus it follows Ernst's trends to rename every little thing where e.g. downvotes are "reduces", except it's more complicated than that bc downvotes themselves still exist - except they don't, in that they don't affect the sorting (or maybe that was the reduces?) - plus they are now publicly visible, except again they are not (actually "boosts" are, reduces are not, and I forget whether they are or not for up and downvotes).

Even at its peak it never topped 1k monthly active users (according to this site), so compared to Lemmy's ~35k the ~0.7k users of Mbin are practically unnoticeable.

PieFed is the new hot thing, with many features that Lemmy lacks, and some even that Reddit itself does not have. It is still being polished but its pace of development is extremely fast! 😁

Mbin is still going strong. We're just not big.