Over the least several months, I've received quite a few emails about Ruby CDK. Many of the questions and comments revolve around the library now being out of date with both Ruby and CDK. Unfortunately, my priorities have moved in a different direction, leaving little time to maintain Ruby CDK.
So I was very happy to hear from Sebastian Klemm, who took on the job of updating Ruby CDK.
If you need to use CDK from Ruby, or you're interested in an alternative to CDK's built-in renderer, I encourage you to check out Sebastian's work.