Below is a link to what I believe is the last official ical source release. Also below is a link to a patch I wrote to get the last ical source release to build with recent versions of gcc and Tcl/Tk. This was last tested with GCC v4.8.2 and Tcl/Tk v8.6.3 under Kubuntu 14.04 (LTS).
I had to make a few minor but substantive changes which have only been lightly tested so use at your own risk. The patch is in the public domain, but proper attribution, while not required, would be appreciated.
My setup includes a custom (but normal) build of tcltk-8.6.3 installed under /opt/tcltk/tcltk-8.6.3. This is highly recommended in order to get a stock Tcl/Tk installation with which ical's "configure" script can work
The steps I use to build ical are as follows:
Newer versions of libc6 cause ical to abort on relatively minor memory allocation errors. To allow ical to run free, export the following environment variable:
ical-2.2.tar.gz (last official ical source release)
ical-2.2.patch.bz2 (for use with gcc-4.3.3 and tcltk-8.5.7)