Ask HN: Recommandation for a self hosted chat system

We currently have an (very) old version of Openfire running on a Windows server.

Before updating it, I would like to know if there is a better (and non JVM dependent) alternative. I found plenty alternative but I would like qualified opinions on them.

We have no budget for this. We don't need fancy features, just something that I can setup and forget (auto update would be a must).

We're currently using Pidgin clients but it's not a problem to use something else. We have a dozen users.

I would rather let it on this Windows server, but I can find a Linux host if it's necessary.

Thank you.