And blogged, with a bit more information and links to JVM spec docs, 
opcode quickref, and more examples:

http://blog.headius.com/2009/03/bitescript-001-ruby-dsl-for-jvm.html

Charles Oliver Nutter wrote:
> BiteScript is a Ruby DSL for generating JVM bytecode and classes. It is 
> used by the Duby programming language and by the upcoming "compiler2" 
> Ruby-to-Java compiler in JRuby.
> 
> Project page: http://kenai.com/projects/jvmscript
> 
> Install: gem install bitescript
> 
> Dependencies: JRuby 1.2 or higher
> 
> Changes:
> 
> * First public release. Most features up to Java 1.4 are supported plus 
> Java 5 annotations.
> 
> Sample code:
> 
> require 'bitescript'
> 
> include BiteScript
> 
> fb = FileBuilder.build(__FILE__) do
>   public_class "SimpleLoop" do
>     public_static_method "main", void, string[] do
>       aload 0
>       push_int 0
>       aaload
>       label :top
>       dup
>       aprintln
>       goto :top
>       returnvoid
>     end
>   end
> end
> 
> fb.generate do |filename, class_builder|
>   File.open(filename, 'w') do |file|
>     file.write(class_builder.generate)
>   end
> end
>