R-Bus is a native implementation of the D-Bus protocol, with these goals in mind:
A lot of things already work and the initial version with docs and examples is available as gems or tar.gz packages. It supports all basic client functionality except exporting objects to a bus. Also, there's a pure ruby version of dbus-send, called rbus-send, included. Since 0.2.0 R-Bus also works with winDbus.
Install with ruby gems:
$ gem install rbus
Get the code from Subversion with:
$ svn checkout svn://rubyforge.org/var/svn/rbus/trunk rbus
The license is GPL.