This is a question without a simple answer. If by "Linux", you mean the Linux kernel, then yes. The source code is available free of cost, and you are free to modify it with only a few restrictions. If you meant "a Linux distro", then maybe. Most Linux distros, such as Ubuntu, Fedora, Debian, and Slackware are available free of charge as well, and with similar rights to modify and redistribute. However, a few Linux distros, such as Red Hat Enterprise Linux or Xandros use a lot of proprietary software, and are not made available free of charge.
There are a variety of different Linux software downloads available for download. One can download basic Linux for free from sites such as Download Linux Free and Softonic.
Scribus Linux Office Suite: OpenOffice [Free] Linux Office Suite: GNOME-Office [Free] Linux Office Suite: KOffice [Free] Linux Office Suite: SiagOffice [Free] Linux Office Suite: StarOffice
Linux and BSD are both excellent and available free of charge.
linux
Linux
Ubuntu Linux.
Linux and the many variations based on Linux (Ubuntu, Mint, to name but two) are aimed at any one who wishes to use it, and is available for free.
Red Hat Enterprise Linux - produced by Red Hat SUSE Linux Enterprise Server - produced by Novell Ubuntu (available free of charge, but has paid support available) - produced by Canonical.
Linux differs from traditional operating system primarily in the fact that most distributions are available free of cost.
There is none. All major Linux certifications (LPI, CompTIA, RHCE, etc...) all cost money.
Most Linux distributions are available free of charge, so they do not require q product key to install.
Linux for Dummies is a great start if you are totally unfamiliar with Linux. If you are familiar enough with Linux, and you have an idea of what distro you want to try / use, you can download a free guide book from Linux-Books.