While DNF is still new and fresh, an initiative is underway in porting it from Python -- the language Yum was originally written in -- and to turn it into a C code-base.
DNF developer Jan Šilhan wrote that the DNF code is slowly being rewritten into C and the Hawkey resolver was merged into the libhif library. DNF already interacts with a number of C libraries like Hawkey, librepo, libsolv, and libcomps. Libhif is designed to be a simple package manager built atop Hawkey and Librepo that's LGPLv2+ licensed.
To learn more about Libhif, see the GitHub project. The initial release of libhif with Hawkey is planned for debut in Fedora 25 later this year. For more details on the DNF C conversion process, read this blog post on the DNF project site.