The Windows tax went away when Amazon launched unix HVM, starting with "cluster compute" instances over five years ago. It has never applied to the FreeBSD images in the AWS Marketplace.

That's interesting, I can recall getting charged although I don't remember the details. I've never used the "official" AMIs, though, so perhaps it was because we built our own. Either way, thanks!

I think FreeBSD has been available for non-Windows Xen HVM instance types on AWS for a while now, maybe cperciva has more details on when this happened.

As soon as EC2 had Unix HVM instances. So every new instance type launched from 2011 onwards.