Not all of them are. The only games that are officially freeware are:
CnCNet provides a ready to go installer for Tiberian Dawn, Red Alert, and Tiberian Sun. The games have been updated to work with the latest operating systems and builds in order for you to get on your way to playing online.
For the games that aren't freeware, CnCNet provides installers which only include the CnCNet developed components required for you to play online. They're designed to look for your game directory and extract the components necessary for multiplayer, as well as applying compatibility fixes in order for you to play with modern day systems.
In order for you to play games such as Red Alert 2 and Yuri's Revenge, you will need to already own a copy of the game for it to work.
CnCNet is not linked to EA, and has no official affiliation with Electronic Arts.
CnCNet is completely free to use, and open source as well. CnCNet is financed by donations kindly contributed by the community.
Yes - the C&C Ultimate Collection works with CnCNet. The CnCNet installers will automatically find your game installation, whether it's the C&C Ultimate Collection, The First Decade, or an old CD install you have.