PyChess is available in a number of different formats. You can get it from source, from the package list below (the recommended method these days, as most distributions are slow to update their pychess packages), or from your distribution's repository. For more information, check out HowToInstall on the wiki.
Fedora / Red Hat / CentOS
yum install pychess, or install the latest noarch.rpm from the package list below
Debian / Ubuntu
apt-get install pychess, or install the latest deb from the package list below
pacman -S pychess
OSX & Windows
While there has been progress porting PyChess to Windows there are not currently any stable releases.
The main issue is the way PyChess communicates with engines which is built tightly around the unix process model. If you feel like helping out, you are heartily welcomed to check You & PyChess, and specifically contact Leonardo Gregianin.