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.
Source:: Linux Kernel