Easy Install Instructions:

1) Install a clean copy of Mozilla 0.9.5.
1b) If you have a copy of Mozilla 0.9.5, ensure you last had the modern skin running. Or, if you've just installed it, run with Modern.

If you can install RPMS:
2) Install the libical RPM as root.

Otherwise:
2) Download http://www.softwarestudio.org/download/libical-0.23.tar.gz , untar and run make / make install

3) Unzip the calendar zip somewhere sensible. You'll need to keep the files around wherever you put them.
4) Edit the MOZ_PATH variable in the "calendar" and "setupcalendar" scripts to point to your 0.9.5 directory.
5) From the calendar directory, run ./setupcalendar.
6) Edit the file content/penglobal/penroot.js and change "/home/mikep" to your home directory.
7) Run ./calendar to run the calendar. 

Head to irc.mozilla.org #calendar to talk about any problems you encounter.