I work on the JRuby project, and have recently (a couple times in the past year) attempted to get Discourse running. It would mean you can run a single Discourse process for a whole site, and probably use less memory and CPU at the same time. I think it’s worth getting it to run.
As with most existing Ruby apps, there are a few missing C extensions.
The good news is that most of these extensions appear to have alternatives for JRuby, or they’re trivial enough that it should be easy to just make a JRuby version.
I wanted to start a discussion here so we can talk about some of the exts and possible replacements.
Any interest in Discourse on JRuby?