My modem has finally a fully open source driver, which is now supported in Fedora Core 3 as it includes ALSA.
A softmodem is really just a glorified soundcard, so ALSA provides the low level support required. The details for my system are:
    $ /sbin/lspci | grep Modem
    00:1f.6 Modem: Intel Corp. 82801CA/CAM AC'97 Modem Controller (rev 02)

    $ grep Modem /proc/asound/cards
    1 [Modem          ]: ICH-MODEM - Intel 82801CA-ICH3 Modem
                        Intel 82801CA-ICH3 Modem at 0x1800, irq 11
The higher level daemon providing the AT commands etc. that interacts with the lower level driver is provided by smartlink.
To build that daemon do the following:
    gzip -dc slmodem-2.9.10.tar.gz | tar x
    cd slmodem-2.9.10/modem
    make SUPPORT_ALSA=1
This package also provides lower level drivers that you will need if you don't have ALSA support for your modem.
Note even if we were building kernel modules on Fedora Core 3 the kernel SRPM is not required.
There is enough present in /lib/modules/$(uname -r)/build as described in the release notes.

To install the previously built daemon, first change to the root user in the "make" directory above:
install the daemon:
    install -D -m 755 slmodemd ${DESTDIR}/usr/sbin/slmodemd
    rm -rf ${DESTDIR}/var/lib/slmodem
    install -d -D -m 755 ${DESTDIR}/var/lib/slmodem
setup the service to be started at each boot:
    echo 'SLMODEMD_COUNTRY=IRELAND' > /etc/sysconfig/slmodemd
    cd ../scripts
    patch slmodemd slmodemd-alsa.diff
    cp slmodemd /etc/init.d/slmodemd
    /sbin/chkconfig --add slmodemd
run the service now:
    /sbin/service slmodemd start
Setup the appropriate devices for users of the modem:
    cd /dev
    ln -sf ttySL0 modem
    cp -a modem /etc/udev/devices
To see the access permissions on the modem device one can do the following:
    $ ls -lH /dev/modem
    crw-rw----  1 root uucp 136, 0 Mar 22 07:31 /dev/modem
This means that any normal users of the system need to be a member of the uucp group to access the modem.
To do that search for "uucp" in /etc/group, and add the required users to the end of the line (separated by commas).