JForum2
Bug fixes and enhancements for JForum 2.x
...Built from the ground up around an MVC framework , it can be deployed on any Servlet 6 container or application server running at least Java 11, such as Tomcat, Jetty and JBoss/WildFly. Its clean design and implementation make JForum easy to customize and extend.
There is extensive documentation of all aspects of the software at https://sourceforge.net/p/jforum2/wiki2/Home/
It is freely available under the BSD license, and has recently been awarded the SourceForge "Community Choice" badge.