The project is now hosted on http://github.com/zenovich/runkit
To install a release version, simply type
sudo pecl install https://github.com/downloads/zenovich/runkit/runkit-1.0.3.tgz
(to install version 1.0.3).
See the http://github.com/zenovich/runkit/downloads for the full list of release files.
To get most fresh and hot features you may also build the extension from master-branch source code. Clone it with
git clone git://github.com/zenovich/runkit.git
and follow the instructions in the README file.