I have noticed that Kubuntu (I am using 12.04 version) doesn't use exactly the same repositories that Ubuntu. Or at least, that is what I think. For example, if I search for Steam on Muon Software Center or Muon Package Manager, I just can't find it; even if I use sudo apt-get install steam-launcher. But on Ubuntu I have no problem. Why?
That's why I think Ubuntu has some repositories that Kubuntu doesn't. In this case (I don't know if I'm right), how can I add this Ubuntu repositories?
Steam is only an example. There are many packages that I can't find on Kubuntu. Another example: Motorbike (a game) (https://apps.ubuntu.com/cat/applications/precise/motorbike/). sudo apt-get install motorbike doesn't work.