[SmirkingRevenge]

True. But I think Kotlin strikes a nice balance of seamless interoperability, convenience, and apparently few compromises. The java interop feels natural - far more natural than it does in most of those other languages you mention (I don't have experience with them all though) - but the language is more concise and convenient than java, even though its very similar. It also has static typing.

Some of the languages you mention come with serious compromises when used on the JVM, like Jython and Jruby - decent portions of their ecosystems are implemented in C - and hence won't work on the JVM.