You can download the current yorick source from github as a tarball or zipball. You may also wish to build additional yorick plugin packages; see the plugins listed on the Wiki.
Compile instructions are in the top level README file; on UNIX or Mac platforms, a simple "make install" will configure and build yorick. On MS Windows, you can build a terminal-based yorick (like the UNIX or Mac yorick) under MinGW (or Cygwin) with a similar make command. Currently, building the GUI yorick on MS Windows requires that you have MFC (Microsoft Foundation Classes), which is outdated and only present if you purchased MS Visual C++. The terminal yorick works equally well, especially if you run it under emacs; yorick interactive graphics windows work, and emacs gives you a place to type commands.
On Debian or Ubuntu Linux systems, you can simply install the latest yorick Debian packages.
There are some outdated binaries for other platforms at the yorick sourceforge projects page. We will post updated binaries as they become available. If you would like to maintain a yorick binary for some platform, please contact dhmunro at users.sourceforge.net.