Actually, I never even thought about https for secure connection! I'll consider this a bug, and will look into it further. Meanwhile, if you have a link with the https, you should be able to add it directly via phpmyadmin. When the links are called from the database, it does not check for https or http, etc. Only when a link is submitted is it checked for valid URL, and as I said, I never took this into consideration when I started TLD.
edit
Just a note, it's just a matter of changing the regexp on the submit_link.php script.
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