If your browser alerted you that the site certificates have changed, that would be because we replaced our StartCOM, Ltd certificates with those offered by our DNS registrar, Gandi. We are very thankful to Gandi for this opportunity.
A common question is why we aren't using the certificates offered by the Let's Encrypt project, and the answer is that there are several technical hurdles (on our end) that currently make it complicated. Once we resolve them, we will most likely switch to using certificates issued by our fellow Linux Foundation project.