Kotlin is build with interoperability with Java in mind from the beginning. This is not the case in Ceylon. In fact some base types (Int, Long) in Ceylon don't match the corresponding Java type. Kotlin has extension methods which Ceylon has not. Ceylon has reified types, which Kotlin has not. Ceylon went 1.0 in November 2013. So far Ceylon seems not have caught any traction, which is unfortunate as it also is a language well-made in many ways. Kotlin has at least Android development to create some initial traction.