The Crubuntu spin aims to be similar to Kali Linux, in that rather than "re-invent the wheel" and create a completely new kernel from scratch, it will follow suit to Kali (e.g. Kali is very similar to Debian for example).
Crubuntu will instead use an already popular distribution - Ubuntu, and its variants e.g. Xubuntu (XFCE-Ubuntu), Kubuntu (KDE-Ubuntu) & Lubuntu (LXDE-Ubuntu) and pre-package the OS with essential tools that a student studying Computer Networking requires to proceed with college coursework, as well as functioning as a everyday operating system.
The reason for using Xubuntu & Kubuntu for a base is that the Ubuntu kernel is among the best supported community kernels available, as well as XFCE, KDE & LXDE being a medium-weight environment allowing for a greater access for usage with older hardware.
As well as being a spin of Xubuntu & Kubuntu, all documentation which applies to the Canonical Ubuntu kernel, also applies to the Crubuntu spin, meaning any specific "after-install" customizations can be done following Ubuntu community forums etc.
This also means that the spin is published under the GNU GPLv3, as is its a spin of its original Xubuntu Kernel with links at the foot of this webpage, and is therefore free to pass-on, alter and improve as you wish.