In the last years the Kotlin programming language for the became quiet popular choice for developing Android apps. It is designed to be interoperable with Java. Mainly it targets the Java virtual machine (JVM).
Also Scala is used for many solutions targeting the JVM.
Are there any suggestions concerning writing Wowza modules with other JVM languages?
Any other experience with that? Side effects to expect?
I tried bumping your question in the Livestreaming Slack, but I didn’t get any responses. Sounds like folks haven’t tried.
Scala I’ve written in the past for multi-agent distributed systems has performed on par or faster than Java. But ultimately its going to come down to what functions you are using and how optimal they are. Not a helpful answer, I know 
I’ve converted a test example for the Android GoCoder SDK from Java to Kotlin in Android Studio and everything worked just fine, but that’s not a production case and I wasn’t stressing the solution, just a simple proof of concept.
If you do end up writing something in Scala or Kotlin, please let us know how it goes!