Fedora 22 is going to require applications that want to appear within their GNOME Software Center to ship an AppData file, which is a meta-data specification for providing basic data about the program. AppData is a GNOME-backed specification based on a subset of the AppStream meta-data proposal. An AppData file comes down to an XML file that specifies the basic program information like the license, name, and descriptions of the program. Screenshots of the program can also be specified via URLs. The AppData specification can be found on this web page.
Richard Hughes announced the forthcoming change on the Fedora development list, "We're introducing this change so that we can show a powerful application full of high-quality content, rather than what we have now which is a equal mixture of awesome and sadness."
The packages will still be in the Fedora repository, but not be offered from the software installer's GUI and only accessible via the command-line. Richard wrote, "A lot of unmaintained or unloved applications will be removed (which is a totally good thing, we don't want new users choosing buggy and crashy apps), but there are also a lot of applications there that we probably want to save. Note that I don't want the packages removed from Fedora; users can still use the command line to install them, just not show them in the 'Software' GUI."
At the moment there's only around 200 packages in Fedora that ship with AppData, or about 11% of all packages. AppData is mostly GNOME-specific but the Fedora developers want it to be cross-desktop. At the moment though there's no Xfce packages with AppData and only about 1% of the KDE packages have AppData, according to data provided by Hughes.