* KDE Frameworks 5, which is a modularized, tiered set of libraries and runtime components that complement Qt with functionality useful to building apps and shells.
* KDE Plasma 5, a set of shells implemented using Frameworks 5. Plasma Desktop is the most prominent of those. KWin is part of Plasma, FWIW, so sure, it's at 5 now.
* KDE Applications. Not yet at 5, but will increasingly ship ports of individual applications to KF5 over the next releases.
Contrast this with KDE 4 development. KDE 4.0 (which contained all of these things in one) came years after the last major release of KDE 3, thus stopping the world cold for its entire development cycle, and e.g. preventing apps from doing feature releases. Separating these things and releasing them independently means that Plasma continued to make 4.x releases during ramp-up of Frameworks 5 development, KDE Applications kept doing feature releases while Plasma 5 is materializing, and so on. It's just a lesson learned from the last round. It's certainly more complex from a "SKU" perspective, but the net effect on users is not leaving them stranded for years. The effect on developers has actually been increased productivity: Plasma 5 development happening against already somewhat-stable Frameworks 5 instead of starting out at the same time, for example.
That does make sense. But it still leaves me a bit wondering what the state of KDE5 is. I mean when can it be considered as released and ready for production? Will Kubuntu ship Plasma5/KF5 next release (14.10) even if the applications are not yet ready?
> I mean when can it be considered as released and ready for production?
A fair question :). Let me summarize:
* KDE Frameworks 5 made its first stable release on July 7th, 2014. That's since been followed by Frameworks 5.1 one month later. It's monthly releases from here on out. This is production-ready code.
* KDE Plasma 5 made its first stable release on July 15th, 2015. This was followed by Plasma 5.0.1 one month later. Plasma 5 does monthly maintenance releases, while feature releases are on a three-month interval, i.e. Plasma 5.1 will be released in October. 5.0 is considered a stable release, but it's a dot-oh with some rough edges (nothing comparable to 4.0 at release, though), and the distros are also still doing their integration work right now. The release notes and an errata list provide some guidance there. Most distros will replace Plasma 4 as default with 5.1 or 5.2 later this year, when everything will have settled nicely.
* KDE Applications is doing a 4.14 feature release this month. This will be the last one built entirely on the KDE 4 libraries. Future KDE Applications releases will start shipping ports of apps to Frameworks 5, at the discretion of their individual maintainers/dev teams (some have had porting branches for a good while).
> Will Kubuntu ship Plasma5/KF5 next release (14.10) even if the applications are not yet ready?
I'm not 100% on top of the plans of the Kubuntu community, but I believe 14.10 is still going to use Plasma 4 by default - you might want to look into that more closely though, I'm not certain. I'm sure they'll offer Plasma 5 for interested users in some form as well though. They probably do already. KDE 4 apps still run in Plasma 5, of course, so that's no limitation (and KF5 apps also run in Plasma 4, for that matter).
Yes, on the promo front this does mean we don't get to do a big "BANG! It's KDE 5!" moment, but it also has some advantages for promo - e.g. driving home that KF5 isn't useful just for making apps that run in Plasma, and by implication that KDE Applications aren't useful just in Plasma.
* KDE Frameworks 5, which is a modularized, tiered set of libraries and runtime components that complement Qt with functionality useful to building apps and shells.
* KDE Plasma 5, a set of shells implemented using Frameworks 5. Plasma Desktop is the most prominent of those. KWin is part of Plasma, FWIW, so sure, it's at 5 now.
* KDE Applications. Not yet at 5, but will increasingly ship ports of individual applications to KF5 over the next releases.
Contrast this with KDE 4 development. KDE 4.0 (which contained all of these things in one) came years after the last major release of KDE 3, thus stopping the world cold for its entire development cycle, and e.g. preventing apps from doing feature releases. Separating these things and releasing them independently means that Plasma continued to make 4.x releases during ramp-up of Frameworks 5 development, KDE Applications kept doing feature releases while Plasma 5 is materializing, and so on. It's just a lesson learned from the last round. It's certainly more complex from a "SKU" perspective, but the net effect on users is not leaving them stranded for years. The effect on developers has actually been increased productivity: Plasma 5 development happening against already somewhat-stable Frameworks 5 instead of starting out at the same time, for example.