The open-zfs.org host, Dreamhost, returns a page for https://open-zfs.org
(note, httpS://) which causes HTTPS Everywhere with the 'Encrypt All
Eligible Sites' option enabled to redirect http://open-zfs.org to
https://open-zfs.org, and therefore fail to redirect to openzfs.org.
Ideally a redirect would be implemented at Dreamhost for
httpS://open-zfs.org too, but presumably the links in the docs should
really be updated anyway.