I bet Apollo is a fairly commonly used name. As one example, Amazon's internal deployment system is named Apollo: http://www.allthingsdistributed.com/2014/11/apollo-amazon-de...

It's probably a stretch to say that Amazon's Apollo has a bigger "market share", because it's not on the market. AWS CodeDeploy may be similar--haven't checked it out. Nevertheless, the Amazon Apollo's user base is probably way bigger than ActiveMQ's or Spotify's Apollo :)

Also, it seems the Greeks have stolen the name for one of their gods too.

Spotify has used Greco-Roman Pantheon names in its technology stack. I don't know all of the exact details for Apollo in this context but I assume similarities to existing tech is coincidental.

I agree, dev team could have shown some creativity in naming the project. As Knuth says, naming matters a lot.