Well, xterm it is a recommended application, sure... it is a console where you can execute commands that you can't play easily in other way. But it is not strictly necessary.

Try first with the original version of the GPE-Calendar (mine it is only a cosmetic change of this version) In order to do that install the official repository for the GPE apps, it is the next one:

Web address [WWW] http://downloads.kernelconcepts.de/maemo3
Distribution: bora
Components: free

And then install the GPE apps from the Application Manager (in this case you don't need the xterm) After that, if you prefer the changes that I did to the applet, try to install my packet and it's posible that you don't have any trouble on this.

HTH