Open Source Operating Systems
Unix
Linux
A Linux distribution is an open source operating systems based around the Linux kernel, which is the core part of the operating system software that is always running on the hardware. While Linux-distributions may operating differently, they are all based off of the same Linux kernel, developed by the Linux Kernel Organization and a community of developers.
Debian
A Linux-distribution composed entirely of open source software, developed by the community-supported Debian Project. Debian is one of the oldest Linux operating systems and is the basis for many other distribution. This operating systems does not require the purchase of a software license for use.
Ubuntu
A Linux-distribution based off of the Debian operating system, developed by Canonical and a community of developers. This operating systems does not require the purchase of a software license for use.
DietPi
Raspbian
FreeBSD
An operating system based on Unix, the predecessor to Linux and one of the first operating systems. Many modern operating systems utilize code first created for use in the BSD operating system.