The main reason that JRuby and truffle Ruby parted ways was due to their desire to support C extensions. We went down that road many years ago and decided that the performance characteristics of the MRI extension API inside a managed VM like the JVM just would not scale, and most extensions are not thread safe or memory safe. In our estimation, C extensions are the biggest thing holding Ruby back. We wish the Truffle folks the best of luck in their efforts to fix their C extension performance and threading problems but they just aren't a fit for JRuby.