The Tiberian Sun Client is a complete, stand-alone Tiberian Sun package for both players and modders. It fixes all known (fixable) bugs in Tiberian Sun and offers a ton of new functionality, including a new easier-to-mod file structure, new game options and pre-defined starting locations and teams. With the Client's bugfixes and enhancements, Tiberian Sun players get a significantly enhanced experience compared to the original game, while enjoying gameplay exactly identical to the original game. For modders starting a new Tiberian Sun mod, it is not required, but highly recommended that you begin with installing the TS Client. The new file structure directly exposes the most critical INI and MIX files of the game, meaning that you don't need to download any special tools for most basic modding.
The latest version of the TS Client that was released today, version 5.40, includes the often-requested Tiberian Sun Demo missions.
Thanks to E1 Elite of Project Perfect Mod for modifying the missions to be usable with the client.