The current JRuby team members are all passionate hackers with intimate knowledge of Ruby, Java, and of course JRuby. That said, none of us were on the team at the project’s original inception. I assume the JRuby pioneers thought JRuby would be a good idea—I know I did, when I first heard about it. For a lot of folks though, it’s somewhat less obvious. Why is writing JRuby on top of the JVM a good idea, they ask. Are we nuts, evil geniuses, or is using the JVM just a solid pragmatic decision?