Getting the latest version of gtkD from the subversion repository
If you have subversion installed on your system you can checkout the latest version from the repository. Open up a terminal, go to the directory where you want gtkd to be after checkout, and run the command:
svn co http://svn.dsource.org/projects/gtkd/trunk
The gtkD svn repository is not always guaranteed to be compilable. It is the bleeding edge, and might be going over some dramatic changes at any random time. If such a thing happens, you should try some of the prereleases instead, or grab an earlier repository snapshot. However, gtkD developers will try their best to keep the subversion repository compilable most of the time.
For more info on subversion and how to use it for development you can read the book. You can then use the forums or the IRC channel #gtkd on freenode to ask the project admins to give you write access to the gtkD repository, if you want to start developing gtkD.