Richard Stallman intended GNU to be a full-fledged operating system, but without a kernel, he couldn't do it. At least until he discovered Linus Torvalds' Linux kernel, thus the GNU/Linux (or GNU+Linux) operating system was born.
As far as open-source projects are involved, both are open-source projects. And you don't have to only use the Linux kernel with GNU, as there's the GNU/Hurd project, and then the ever-popular Android (runs on a modified Linux kernel, the remaining are developed by Google)
Both of them are operating systems.
yes
An operating system is the system working on the computer. Linux and Windows are both operating systems used in businesses.
Linux and BSD are both excellent and available free of charge.
Redhat and Mandrake are not versions of any operating system. Both are itself standalone Linux operating systems.
No, OpenOffice is a productivity suite similar to Microsoft Office. Linux is an operating system (as is Microsoft Windows). Both have in common that they are Free Open Source Software (FOSS), which means they are free to download and are free to change (because the source code is provided). OpenOffice runs on Linux as well as Microsoft Windows or Mac OS X and some other operating systems.
NetBSD, Windows, and Linux each support both FAT and NTFS file systems.
If one or of the operating systems does not cooperate well with dual-booting (such as Windows with a Linux distribution), then you should install the troublesome operating system first. If both are well-behaved (such as two Linux distributions) then it does not generally matter.
Open source (free) software (Operating Systems based on the Linux kernel: Ubuntu, Linux Mint (to name my two favourites) are, in my opinion, the best OS software to use. Both come with many free application software programs for the downloading off the internet.
When you network operating systems you will have the benefit of both operating systems. You have to ensure both systems are compatible before networking them.
One of the best free operating systems is Linux. It does pretty much everything Windows can do, but there is no cost to own and operate it.
Linux or Unix are open source and some are versions are free and others aren't. Unix is based off of Linux, and both have many different variations. One popular Unix system is Ubuntu