Ruby+OMR is developed in three pieces: 1) the language independent core, then 2) The language dependent portions (i.e., the VM, and what we call the 'glue')
The language independent core is here: https://github.com/eclipse/omr. It's under active development, :)
I'm actually working on Ruby 2.4 support right now (supremely not prime time, but if you're curious, the branch is here: https://github.com/mgaudet/ruby/tree/ruby_2_4_omr_preliminar...)