Configuring LogBack using an internal DSL with Groovy is a clever idea.

Rather than including logback.groovy in the classpath and requiring a 5.5 MB groovy-all dependency to load and interpret it, why not offer a way that logback.groovy could be compiled at compile time. Then, instead of interpreting logback.groovy using a GroovyShell, why not simply run a method from an already compiled class.

This strategy has the advantage of discovering many configuration problems (like typos) at compile-time rather than run-time.