You Can Download Linux (And Applications) For Free

Because of the open-source nature of Linux, almost all distributions are available for free over the Internet. There are limits to this, since most distributions fill up at least one CD (650MB) and some take up as many as five. You need a pretty fast net connection to make this practical.

However, you can also download parts of distributions as well. You can download a usable, if minimal, system without tying up your modem for weeks. This also allows you to upgrade parts of your system (including the kernel) without having to buy another CD. The Debian distribution, for example, is designed to be upgraded automatically in just this manner. This can dramatically reduce the cost of maintaining a system.