Dotruby is a project mainly written in Ruby, it's free.
Definitive Ruby Project/Package Metadata
DotRuby (.ruby) is a well-defined Ruby project/package metadata file format.
A .ruby file has a very strict specification. The specification is simple enough for Ruby developers to work with the file format directly.
DotRuby project also provides a conveneient API for working with a .ruby file and it data.