Many parts are written in C using Cython, and tested with regression tests.
But you can’t download the packages from Debian Package Manager.
Yum is implemented as libraries in the Python programming language, with a small set of programs that provide a command-line interface.
As a full rewrite of its predecessor tool, Yellowdog Updater (YUP), yum evolved primarily in order to update and manage Red Hat Linux systems used at the Duke University Department of Physics.
Then you can install : you can get versions up to v8.5.2 from my repsitory, but you have to active Debian's backports repository if you want to install the GUIs as they're linked against a newer version of Qt than wheezy itself contains.
My GPG key's ID is 16D2F5DC 10C052A6, and the fingerprint is EB24 BCA1 4BA6 A24F 1427 6FEE 16D2 F5DC 10C0 52A6.