As an Eclipse plugin, the typical installation procedure is via the update site.
XTypeS requires Xtext 2.
You can install XTypeS plugins directly from the update site (of course this requires Xtext 2.0 SDK):
From the update site you can also install the Examples, and the SDK (which basically contains the sources of XTypeS and of the examples).
Sources can be obtained via git (which can be browsed online); you can clone the git repository of XTypeS with the following command
git clone git://xtypes.git.sourceforge.net/gitroot/xtypes/xtypes