Tiberian Sun: UMP (Unofficial Mini-Patch) is like a base for new mods, it fixes all known (fixable) bugs in Tiberian Sun. The UMP also implements all Firestorm features into Tiberian Sun, so rather than modding Firestorm, you can just mod Tiberian Sun instead. Before starting any Tiberian Sun mod, it is not required, but highly recommended that you begin with installing the UMP.
When modding with the UMP base, you are to edit rules.ini and art.ini, you are not to edit firestrm.ini and artfs.ini, leave those blank as they are in the UMP. They can be used for something else at a later date if you desire.