I've removed Fedora 10 and 11 from the supported OS list, as they have been EOLed by the Fedora project. 12 and 13 have never been added to our repos or supported OS list due to very low demand for Fedora (and with very good reason; Fedora, like Ubuntu in non-LTS releases, is a terrible choice for servers because of its extremely short lifecycle).
But, because Fedora has been supported in the past, and there may be a few stragglers with systems running Fedora, and because it is actually the easiest OS to support of all Linux distros, I thought I'd ping you guys and see if there is a demand I'm just not aware of for running Virtualmin on Fedora. I know there's at least one ticket about it in the issue tracker, so there's at least one user wanting to do so.
So, let me know, keeping in mind that any OS adds a development burden that takes away from other tasks. If you could just as easily use CentOS for your projects, then maybe you'd be better off with my development time going to making the bleeding edge CentOS repository bigger and more interesting (for example).