You will need to build a scalix-tomcat-connector package that satisfies the dependencies the scalix-tomcat package has on it, but works on fc5 and Apache 2.0. Very likely, the package for RHEL4 can be a good starting point or might even work (not sure about the compatibility of the exact Apache version though)
If you have that as an RPM, the rest of the Fedora Core 5 install should just run fine, just go for a customized install and don't reinstall/upgrade the connector package.
Of course, this will be somewhat messy and unsupported. And all that to get the worst web design package on the planet running?
Florian.