If Gradle's configuration API was opened up so other languages besides Groovy were allowed, such as Clojure, Scala, JRuby, and even Jython, Gradle would attract a lot more developers who are put off by Groovy. Even Gradle's website and promotional materials avoids using the word "Groovy", instead saying "Gradle DSL", but that's not enough to win over hardcore Python or Ruby shops.
As for your case and many others already reluctantly using Groovy in Gradle, translating it all from Groovy-Gradle to, say, Ruby-Gradle wouldn't take weeks but hours because only the syntax would need to be translated almost one-to-one, leaving all the Gradle configuration names and sequences unchanged. In fact, because it could be done incrementally, only minutes spread out over several days.
As for your case and many others already reluctantly using Groovy in Gradle, translating it all from Groovy-Gradle to, say, Ruby-Gradle wouldn't take weeks but hours because only the syntax would need to be translated almost one-to-one, leaving all the Gradle configuration names and sequences unchanged. In fact, because it could be done incrementally, only minutes spread out over several days.