I have updated the key used to sign the openmolar apt repositories (for debian and ubuntu dists).
To install these keys please do the following.
~$ wget https://openmolar.com/rowinggolfer.gpg.key
~$ sudo apt-key add rowinggolfer.gpg.key
~$ sudo apt-get update
Many thanks, and apologies for any inconvenience caused by the expiry of my old key.