The fundamental difference between Red Hat Advanced Server or Enterprise Linux and Fedora is that Red Hat Enterprise Linux is meant for commercial use, while Fedora is for the developer community and for those that want Linux for personal use.
Fedora is not supported by Red Hat (in an official capacity), though they do provide direction to the Fedora Core project. One can say that the Fedora product is now the free Red Hat distro, as they certainly support the open source community with this distribution. It is an operating system and platform, which is free for anyone to use modify or distribute.
This was first published in December 2005