That's actually a very good question. Why does Debian have a yum installer? Well, because some developer believes he can make it work. Unfortunately, he/she hasn't perfected it. Just because a package is there, doesn't mean it doesn't have a lot of bugs, and, yum commands in Debian, as well as deb/dpkg/apt commands in Fedora/OpenSuse/Mandriva have a lot of bugs. And, even though alien has been around for a long time, I've personally never heard a good review of it. If you mention it on any Debian based forum, the answer is "Don't use it". If you mention it on a Fedora forum, the answer is, "Don't use it". So, if you're advised not to use it on forums that use either .deb or .rpm packages, the two package types that its suppose to work with, go with the advise, don't use it. Use what works. Use .deb with .deb based distros, and, use .rpm on .rpm based distros.