You do not relinquish your copyright at any time. The Miller's TOS for Web Hosting only describes web hosting in legal terminology. We are in the process of re-writing this to make it more plainly worded.
Are you referring to this page (http://www.millerslab.com/files/policy/termsofuse.htm)?
You are solely responsible for all materials, whether publicly posted or privately transmitted, that you upload, post, e-mail, transmit, or otherwise make available on our Site ("Your Content"). You certify that you own all intellectual property rights in Your Content. You hereby grant Miller's, our affiliates, and our partners a worldwide, irrevocable, royalty-free, nonexclusive, sublicensable license to use, reproduce, create derivative works of, distribute, publicly perform, publicly display, transfer, transmit, distribute, and publish Your Content and subsequent versions of Your Content for the purposes of (i) displaying Your Content on our Site, (ii) distributing Your Content, either electronically or via other media, to users seeking to download or otherwise acquire it, and/or (iii) storing Your Content in a remote database accessible by end users, for a charge. This license shall apply to the distribution and the storage of Your Content in any form, medium, or technology now known or later developed.