VMware Server is free, but you can buy the support (gold/platinium)...
If you want you can buy, VirtualCenter for VMware Server,with this produc, you can manage one or more VMware Server
It depends on which product you're talking about, and what you mean by "free". For example, Player and Server are available at no cost to you; in contrast, ESX, Workstation, and Fusion cost money.
Some people make the distinction between no-cost-to-you free and heres-the-source-code-have-fun* (* - possibly plus some restrictions) free. We might have a couple modules or tools covered by the GPL and which fall in the second category, but our products in general are not GPL'd.