I know POGS was whitelisted before they had https, but maybe we're more strict now. I also don't know the requirements. They're probably buried somewhere in the main forums, but I'm too lazy to dig :-)
This topic will be discussed at this Saturday's Gridcoin hangout. I posted a comment, basically copy/pasting your original comment from pepper's post. I'll give you the proceeds of that comment, if it happens to get upvoted.