> Open sourcing anything at Google tends to be rather difficult because much of the technology we build is built on other technology that has not been released

Monarch might be an exception to that, though, because - as noted in the paper -, it has to be built without many dependencies, since almost everything else depends on it for monitoring and alerting.

That being said, I'm sure it would be extremely difficult to open source now since it was never built with open sourcing in mind.