There's also XenServer that's free as in beer and speech. But the freedom in speech is mostly theoretical, because it's so hard to build.
Re:VMWare Screw Customers
by zacgarrett on Wednesday July 13, 2011 @12:21PM
(#2759438)
XenServer is actually the product name from Citrix. Xen is the open source project that is Open Source.
I know its being a stickler for the tiny facts, but when you are a XenServer admin find the differences rather quickly.
Xen is a hypervisor. XenServer is the product name from Citrix which uses Xen underneath. Xen Cloud Platform is actually the name of opensource xenserver.
You wouldn't use just Xen as a hypervisor, in most cases. Amazon uses Xen plus their own stuff on top.
To make it more complicated, there's also XenClient, which also builds on Xen. It's also mostly open source.
Alternatives to VMware like KVM aren't just a better version of VMware that happens to be free, but it's fundamentally better because it is free (as in speech, of course).