The Fedora Project (http://fedora.redhat.com/) is basically the free (as in money) Red Hat Linux. It is owned by Red Hat and is the version used as the filtering and testing ring for Red Hat Enterprise Linux. Contrary to common belief, it is not awful. It has reasonably current packages but is quite stable within any given version. Expect multifarious difficulties when upgrading between versions, however, as Fedora enjoys being absolute cutting edge, and often renames packages unexpectedly. Some would recommend this distribution to a new user; however, it is not recommended for use in production, customer-facing servers as support for the OS and its packages is expected for many years beyond Fedora's willingness to support old versions. Its main competitor is Mandriva (see MandrakeLinux).
There are different versions of Fedora, numbered 1, 2, 3 etc. The current latest release (March 2008) is version 8.
There was a Fedora Legacy Project at http://fedoralegacy.org/ which maintained security updates for older releases. This shut down in February 2007. There was never support there for Fedora 6 and the recommendation is to update or use something else if longer term stability is needed.
ScientificLinux is a RedHat related free distribution.
The experimental compiler providing VariadicTemplatesForGnuCpp is available for Fedora Core 4 and 6. (Now of historic interest only as version 4.3 contains variadics.)
Upgrades are going to be necessary from time to time owing to the relatively short support life of Fedora.
http://docs.fedoraproject.org/release-notes/f8/en_US/sn-Installer.html#Upgrade-Related-Issues gives some description of the problems when upgrading from Fedora before Fedora 7 to Fedora 7 or 8. The way in which partitions are described has changed in a way which makes invalid the default procedure used before Fedora 7. The upgrade process complains and then stops. The safe solution to this is to back up all third party work and do a fresh install. -- JohnFletcher
I have used versions of Fedora on several computers, usually installing it by partitioning the hard drive and installing it as a second operating system alongside Windows XP. One laptop I had done this on, recently stopped functioning, although the hard drive was still intact. I removed it and installed it in a USB enclosure to recover the information. To my surprise, another Fedora installation could not see the second installation. This is because Fedora installs as a logical volume (LVM) and they all have the same default group name, VolGroup00, so the second one is silently ignored. It is possible to rename the second group and it then becomes visible again. -- JohnFletcher