Linux
Thank you to the Linux Fanboi journalist for mentioning that Linux is running on the non-critical camera platform.
The tech-brief obliquely mentions VxWorks which is used for the critical parts of the landing platform (including the cameras involved in the actual landing operation.)
VxWorks often runs in hypervisor mode and can run itself, Linux or other OS as virtual machines.
Anon because ... ... I couldn't possibly comment!