Just so you know, the security certificate doesn't mean much.
Having a valid one just means that the company has either registered for one (or, in the case of DanceSafe.org, hasn't renewed theirs) from a Certificate Authority like VeriSign.
If you look at the URL when you go to their store, it's still HTTPS meaning it's secure and encrypted. The certificate is just supposed to help assure you that the company running the site is who they claim themselves to be (ie. that they actually ARE DanceSafe.org).
I highly doubt that someone is spoofing their domain name and that when you go to their site it is them, so you're fairly safe in ordering from them if you want a kit from there.
I plan to get a kit from there sometime in the near future too.