Originally on Gradle.org's website, they wrote they'd encourage anyone who wanted to enable Gradle to allow another scripting language for writing build files, and that they'd help them with bundling it. But since Gradle 2, it looks like too much of Gradle's own source and plugin code is written in Groovy for that to still be feasible. Gradleware also employed one of the former developers who used to work on Groovy when they were retrenched by VMWare a year ago, and I suspect he'd actually sabotage any outside attempt to make Gradle polyglot, like, say, Vert.x is. So it looks like you're stuck with Groovy if you want to use Gradle. With the good comes the bad, as they say!