The total number of active users in the last month would be a much more accurate statistic. The number of users does not give the correct result due to bot accounts.
Its a completely different link agreggator software. But since both Lemmy and kbin are based on the ActivityPub protocol, instances of both can federate with each other. Hence, lemmy users can see content posted on kbin instances and vice versa.
The goal of Kbin is to communicate with many other ActivityPup services.
Lemmy: Link aggregator, social network, forum
Kbin: Link aggregator, social network, forum, microblogging
Mastodon: Microblogging
You can use Kbin to interact with Lemmy, Mastodon, Pleroma, Peertube, and others. That's why I switched today (and loving it, exploring everything right now).
I don't believe that there are multiple instances of Kbin right now. I only know of kbin.social (it is free and open source, though, so anyone can open another instance, I think). Edit: This was wrong. There are many instances. See the answer below.
AFAIK kbin is way early in development and got slammed by a wave of new users after Rexxit happened.
So the dev’s priority right now is server and platform stability, and it’s already way smoother than it was a couple weeks ago. That being said, there are a ton of features planned and development seems to be going pretty quickly at the moment
Ernest, from what I've seen, has been very receptive and passionate about all the incoming users. They scaled their infrastructure quickly to meet demand and were interacting with users on kbin regarding features they would like to see. I have high hopes.