This one time, at Savvis, there was a piece of software that ran in production, but it was past its life. No one had the source code, no one knew how to reconfigure it or update it. It was designed as a flexible middleware, but all it did now was sit between two production systems, translating messages. They couldn’t even move it to a different server because no one knew how to reconfigure it and get it running again. If it went down, they kicked it and hoped it started up again.
This software was undead. Running in production, its execution continued, but without code or any way to change, it was not alive. Beware the zombie middleware!