Here is a brief summary from the web site:
iCalBuddy is a command line utility that can be used to get a list of items (events, tasks, todos) from the Mac OS X calendar (iCal).
Ali Rantakari, the creator of iCalBuddy, suggests that if you are going to use iCalBuddy with GeekTool, to try his custom build of GeekTool, which includes features, like ANSI escape sequence formatting support (like colors, bolding, underlining, etc.) and Unicode (UTF-8) support (used for displaying non-ASCII characters like umlauts, Arabic or Hebrew).

To download the iCalBuddy GeekTool 2.2.1 unofficial hasseg build, click here. There is also more information about the features you may find useful.
Note: There are two versions.
2.2.0 requires Leopard.
2.2.1 requires Leopard OS X 10.5+

In order to install it, do the following: (from iCalBuddy web site)
1. Extract the files from the zip archive by double-clicking on it in Finder
2. Double-click on the GeekTool.prefPane file icon in Finder to install it
3. If you already had GeekTool installed, System Preferences will ask if you want to replace it. Select “Replace”, quit and restart System Preferences and open the GeekTool preference pane, verifying that the version label now says “unofficial hasseg.org build.”
4. Unselect the “Enable GeekTool” checkbox in order to kill the old version’s background process, and then select it again in order to run the updated one.

Below are documentation links from the iCalBuddy website. It is filled with information. And if you have any questions, you may contact Ali Rantakari (which I have done when I first used iCalBuddy) and he will respond to your inquiries (or at least he responded to mine).

iCalBuddy Manual Reference Page

iCalBuddy Config Manual Page

iCalBuddy Localization Manual Page

FAQ Page

Here is the email that I sent to iCalBuddy:

iCalBuddy Response:

I hope that this article helps you understand a little bit more about iCalBuddy and know that I’ve been there with the frustration of trying to figure a tool out. If any of my readers have used iCalBuddy and have any tips or experiences with it, please, feel free to leave a comment and spread the wealth!
-TINA