I use Kotlin without a license. Just the community version of the IDE, they also released an eclipse plugin that is currently unmaintained. But still open source. I think they did their best to help but without hurting their business model.

Groovy has no Netbeans support anymore. Who is to blame. Groovy? Groovy is better as a PL than Kotlin. But Kotlin is no match in terms of performance and pragmatism. I use both instead of Java and I never looked back.