The scope of their self-developed tool doesn't seem very large, it looks like it could be a wrapper around SSH. I've done similar things using a SSH library with python to deploy and run docker-compose yamls on multiple servers.
There are many of these tools out there. When I was working for Technicolor Virdata some years ago, we’ve been heavily invested in https://github.com/infochimps-labs/ironfan. It was extensible, we had support for SoftLayer and IBM SCE, we had some patches to make the bootstrap and the kick command perform faster. But it was still slow and people didn’t like Ruby (I don’t mind it).
Even back then I wasn’t a fan of doing a proactive ssh connection to the node. I always leaned towards the machine pulling artefacts and deploying them. Like Flux CD does.
