It is a preview of the next major version of Yum [1]. It does package management using rpm [2] libsolv [3] and hawkey [4] libraries. For metadata handling and downloads it utilizes librepo library[5].

DNF and all its dependencies are available in Fedora 18, Fedora 19 and the rawhide Fedora. It is not straightforward, albeit possible, to use DNF with Fedora 17 and earlier, unless you are able to update rpm and libdb to the Fedora 18 versions first. Might warrant rebuilding rpm database so know what you are doing and do backup.

[1] http://yum.baseurl.org/
[2] http://rpm.org/
[3] https://github.com/openSUSE/libsolv
[4] https://github.com/akozumpl/hawkey
[6] https://github.com/tojaj/librepo