For me this is the bigger problem. With Groovy and to a lesser extent Kotlin I can write code and ship a library and the consumers don't even know it's source

For me this is the bigger problem. With Groovy and to a lesser extent Kotlin I can write code and ship a library and the consumers don't even know it's source is Kotlin. But it's much harder with Scala. Especially with Groovy you are really not leaving the Java ecosystem at all.