Some users might bit under a misconception what KCP is about, so let my give you my opinion.
I divide it stereotypical into two user-approaches:
The GUI User
You use an app with a graphical user interface to de/install and search for software. Octopi is your friend.
In the systray you will find a little symbol indicating if your software is up-to-date or not. Open Octopi and search within it for the software you need.
KaOS strives to deliver the latest upstream version possible. If you still find that you software is outdated, feel free to search for it in the Online Package Viewer and flag it as outdated. As long as nothing major blocks it, within a few days you will see the new version.
If can't find your needed Software, try hitting the alien-button in Octopi and search again to see if the community has filled the gap.
If you still can't find your needed software that way, than sorry: KaOS might be not for you.
The CLI User
KaOS uses Pacman as package manager (like OpenSuse uses zypper, Fedora uses dnf, Debian uses apt-get and Gentoo uses emerge).
And to say this beforehand (as said many times, see the FAQ): KaOS is NOT another Arch based distribution!
Even if KaOS uses pacman it is not Arch Linux. Fedora ain't CentOS either.
To get software, you will need PKGBUILDs. These are like recipes for your software.
You create a PKGBUILD for the software you need.
- This package script is written by humans
You build the package (the things called *.pkg.tar.xz).
- This does makepkg for you
- makepkg belongs to pacman
- More information about building you packages can be found in the Packaging Guide
You install the package (application.pkg.tar.xz) with pacman
- so pacman can manage the new software for you like the rest of your installed software (hence, package manager)
You can find all PKGBUILDs of the KaOS-repos core, main, apps on GitHub.
For the official repositories, the packages are already build for you, so you just have to download and install them. This does pacman (or Octopi as frontend) for you.
You are free to install every software you deem necessary.
As KaOS uses pacman like Arch, Chakra, ... some (or better: most) PKGBUILDs are usable after slight modification (dependencies might be named different, adjustment to the python or qt, ...).
Sometimes, you come across software where you think, every user of KaOS might profit from it. And here comes KCP in.
KCP (KaOS Community Packages) offer ready-made PKGBUILDs for KaOS, with the benefit of tight integration into Octopi.
If you want to offer the software for all user, you can apply for a KCP-membership. You become de-facto a maintainer for your (and if you want, every other) software in KCP.
Please note that if you do this, you are willing to update your PKGBUILD. The power of KCP also lies in the tight integration with Octopi. If a new version of your software comes out and you update the PKGBUILD, every user will get the new version. In Octopi, the steps build and install are automatically done for the user. The community creates the PKGBUILD.
The thing is: KaOS, is a lean KDE Distribution. Thousands of packages (and therefore thousands of PKGBUILDs) are not the goal of KCP! Then you're better of with OpenSuse, Fedora & co.
If you can find a good PKGBUILD elsewhere and it works, there is no reason to upload it to KCP. If you are like the only one using the software, no reason to upload it to KCP. You're free to do with your installation of KaOS what you want. Just keep in mind: things might break. You need to know what you do.
Sometimes, good old KDE4-apps are missing in KDE Applications (Plasma 5). For example at the moment krename. A "KDE-approved" successor is missing. rkrenamer might be a good alternative, and can be found in KCP. It's Qt-based and fits therefore perfectly into a Qt\KDE-oriented distribution like KaOS.
This is, why KCP exist.
Another good reason might be, that there are PKGBUILDs for the software in other pacman-distros, but the adaption to KaOS is heavier. But please keep in mind: will every user profit from it? (Sorry, but I don't perl-modules for bioinformatic ;) )
If there a doubts, just open a new thread and ask. Be polite, show that you know what you're doing and ask if what you think and want is good.
Blindly uploading to KCP and then rant when your PKGBUILD gets removed... helps nobody.
The things said above are my personal opinion on these. The admins and maintainer of KaOS have the last word! Period.
Nothing is set in stone so some things might change over time. Please read and think further. Thanks.
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EDIT: Corrected the distribution comparison