How do programs make it into the Software center?
There are two ways for an app to get to the Software Center:
- It could be part of the normal repositories: Main, Restricted, Universe and Multiverse. The first two are maintained by Canonical. Universe and Multiverse are a community effort. The best way to land there is to either convince Canonical or Debian that your program is valuable.
- You can add it through the Canonical developer program. This works quite similar to Apple appstore. You will need to provide the source code and Canonical will review it. This is also the only way to add pay apps.
PPA's are no way related to this, they are independent, they get no review but from the person who set it up. Sometimes, Canonical workers, or package maintainers (the members of the community responsible for some part of the Universe and Multiverse package) can setup a PPA (the Mozilla team does), then some packages from this PPA will likely become official packages. But most of the time complete independent people set a PPA, they have no review policy and their packages will never be part of the official repositories.