Hendrik:
...
> You found a little more than I did. Running this package on a wheezy
> system is probably the easiest way to read the calendar. But exporting
> it to a modern file format is likely another matter.
>
> I managed to find the wheezy source package. But the way the word has
> changed, it may be easiest to use the binary package on a real wheezy
> system thatn to try to build the package in a modern system.

I have in my archives:
gpe-calendar_0.91.orig.tar.gz
gpe-calendar_0.92.orig.tar.bz2
in case you want them.

The first one gives on configure:
No package 'libgpewidget' found
No package 'libgpepimc' found
No package 'libgpevtype' found
No package 'libeventdb' found
No package 'esound' found
No package 'libxsettings-client' found
No package 'libhandoff' found
No package 'libsoup-2.2' found
No package 'libsoundgen' found
No package 'dbus-glib-1' found
No package 'libschedule' found

> I'm still exploring alternatives before taking action.

The best bet is to set up a wheezy system and go from there.

> For past events, I'd be happy with a complete, readable text file. I
> might be able to write a program to produce that if I find a compatible
> version of sqlite, or if current sqlite will upgrade the db to whatever
> it uses now.
...

There is no dependancy on sqlite:
$ find . -type f | xargs grep sql 
./ChangeLog:    * configure.ac: Remove dependencies on sqlite and mimedir-1.0.
./ChangeLog:    (do_import_vevent): Don't open an sqlite session, insert directly
./ChangeLog:    * Makefile: Don't link with -lsqlite.  Use STANDARD_CFLAGS,
./ChangeLog:    * familiar/control1 (Depends): Remove libsqlite0.  Add 

Regards,
/Karl Hammar

-----------------------------------------------------------------------
Aspö Data
Lilla Aspö 148
S-742 94 Östhammar
Sweden
+46 173 140 57