I have found out there exists a Linux distro called Winux and formerly known as Wubuntu and Linuxfx. It is based on Ubuntu, which, at the moment, mostly consists of GPL licensed components, so aren’t Winux’ creators obliged to publish their source code?


Only for the components that are GPL. If its based on Ubuntu, then all the Ubuntu packages are compliant.
Their desktop UI may not be GPL though, so they wouldn’t be obligated to share the code. As long as they were disciplined and didn’t statically link a GPL lib, they are in the clear.
Afaik they have KDE Plasma with tweaks