The Fedora Project was set up as a proving ground for developing technology that can be used by Red Hat, Inc. to include in its Red Hat Enterprise Linux products. You can look at Fedora Core 3 as a way of getting a jump on technology that is slated to be included in Red Hat Enterprise Linux and related Linux distributions.
Although the timing of the releases of Fedora Core 3 and the next release of Red Hat Enterprise Linux may make some version numbers different, there are hundreds of software packages that will probably be the same in the two distributions.