There are no royalty or licensing fees for using Linux, and the source code can be modified to fit your needs. The results can be sold for profit, but original authors retain copyright and you must provide the source to your modifications.
Because it comes with source code to the kernel, it is quite portable. Linux runs on more CPUs and platforms than any other computer operating system. The recent direction of the software and hardware industry is to push consumers to purchase faster computers with more system memory and hard drive storage. Linux systems are not affected by those industries orientation because of it capacity to run on any kind of computers, even aging x486-based computers with limited amounts of RAM.
Linux is a true multi-tasking operating system similar to its brother UNIX. It uses sophisticated, state-of-the-art memory management to control all system processes. That means that if a program crashes you can kill it and continue working with confidence.
Another benefit is that Linux is practically immunized against all kinds of viruses that we find in other operating systems. To date we have found only two viruses that were effective on Linux systems.