Groovy AST Transformations
Hamlet is a committer on the Groovy and CodeNarc projects, and is a contributor on a few other open source projects (including JConch and the IDEA Groovy Plugin).
Peter is a long time Java developer and one of the core Grails committers. He has been developing with Grails since version 0.2 (give or take 0.1). He created the GWT Grails plugin as an exercise to see whether it was possible, but it has since grown into something that can support serious development.