Yep, Mandrake (the company) merged with Lycoris and Conectiva to form Mandriva. There are free-of-charge versions of Mandriva available, as well as paid-for versions (called Powerpack) that include technical support and some non-open source components. They also have the Mandriva Club that you can subscribe to for a small monthly fee.
Their Wikipedia page is pretty comprehensive...
http://en.wikipedia.org/wiki/Mandriva_Linux
To go back to the point Sheridan made, there are indeed different versions of Linux - these are the so-called "distributions". Linux itself is the actual kernel, i.e. the core operating system. Briefly, all distributions use the Linux kernel (albeit some will be using slightly later versions of the Linux kernel than others) and then the distribution maintainers will add on the extra applications that they want to include. It's this that differentiates one distribution (or distro) from another - but at the heart they all use the Linux kernel.
There are hundreds of different distros available - have a look at
www.distrowatch.org to compare them - but they are mostly all just variations of a handful of base distributions, such as Debian, Red Hat, Slackware. For example, Ubuntu is a modified version of the Debian distribution, whereas Mandriva is based on Red Hat, whilst SabayonLinux (the distro I'm currently using) is based on Gentoo.
There's no definitive "better" or "worse" distro... it's all down to personal preference. The great thing about Linux, though, is that you're free to choose whichever distro you want - in fact, this is the best way to learn about the differences between each one, and it won't cost you a penny to switch from one to the other. As they're all based on the same Linux kernel, however, you won't struggle if you do decide to switch distro as they all work in pretty much the same way... there are slight differences, for example, in how you install software in one distro that uses package management compared to another where you compile stuff specifically for your environment, but the underlying mechanics of the operating system remain the same from one distro to another.
Hope that helps
