It may also interest people here that the guidance system is written in Haskell. I originally saw this on Reddit, where one of the authors provides a bit more information on the technical aspects of the system [0].
As I mentioned in the reddit comments we're using Haskell for most parts of the system (frontend via GHCJS, web application servers, protocol implementations). For dev-ops we use the Nix ecosystem: NixOS & nixops.
[0] http://www.reddit.com/r/haskell/comments/3959r0/haskellbased...