The introduction of the Welcome application mentions the term GNU/Linux. It would be great to have a few sentences added about what the GNU Project is about and how it is related to the many distributions (how much GNU is there in Ubuntu MATE?) and the Linux kernel.
Perhaps a chart could be added with proprietary operating systems such as Windows and MacOS on one side and GNU/Linux distributions such as Parabola, Trisquel, and gNewSense on the other side. Ubuntu MATE probably occupies a middle ground between them, providing only as much freedom as convenient. It seems to me that Ubuntu MATE subscribes to a freedom of choice model which is perhaps closer to technical freedom ("I can install any software I wish no matter whether it is based on a closed or open source development model") than to ethical freedom ("I only use free software even though it creates inconveniences for me").