Just to clarify, the Killer App mod is not a true patch, in the sense of the word. It's a mod that can be enabled and disabled. A patch is permanent.
However, the mod does fix some things and add new features.
Everybody needs to be using the mod, in order to play online together. If you're the only person using the mod, you won't see anyone else online until you disable the mod. This is explained in the documentation that came with it.
There's another version of the mod coming out in the future, with additional improvements. When it does, we'll probably see some people using it. But for now, the current version has been withdrawn from circulation. If there are any sites still hosting it, it's because they've ignored requests to remove it.
The new version IS being worked on, despite appearances to the contrary. But progress has been very slow, due to real life concerns for some of the team members involved.