Install with:
$ gem install maruku
Gentoo: http://packages.gentoo.org/packages/?category=dev-ruby;name=maruku
Debian: http://packages.debian.org/experimental/interpreters/libmaruku-ruby
The development site is http://rubyforge.org/projects/maruku/.
Released files can also be seen at http://rubyforge.org/frs/?group_id=2795.
Anonymous access to the repository is possible with:
$ svn checkout svn://rubyforge.org/var/svn/maruku/trunk
Also, each version has a tag:
$ svn checkout svn://rubyforge.org/var/svn/maruku/tags/0.5.6
If you want commit access to the repository, just create an account on Rubyforge and drop me a mail.