The way Google builds software makes that approach tough.
Even if you had the source code to the app (which Google isn't about to give out at any price), what you'll find is that it's an app architected to link against libraries nobody has ever seen and run atop a distributed computing fabric that's loosely related to Kubernetes but, really, nobody's ever seen, storing data to a backing store nobody's ever seen, and identifying users via an authentication model that nobody's ever seen.
Dangling references all over the place, leading to special sauce Google is even less likely to publish, because it's deeply tied into a physical hardware architecture that Google can't publish, because even if they did nobody's going to build it.
Some of Google's user-facing stuff runs on the architectures they make public, like GCP. But a lot of it runs on Google's proprietary fabric of service management and distributed storage, which is an alien planet relative to the world outside their walls. Publishing an app out of that part of the ecosystem would be like Google handing a company a koala with no eucalyptus trees. It'd be dead in days.
