This is a good occasion to read the source code of a non-trivial piece of Go code. The documentation of the project seems rather sparse, but at least, the app has readable tests.
That said, if you are looking for an open-source platform as a service, OpenShift, or as others mentioned, CloudFoundry are more mature options.
I had the same impression. I have been working on a very early prototype of something very similar to this and was curious the know the general architecture of the system but there doesn't seem to be any documentation covering that.
I wish that more of these projects were more general like Mesos as opposed to just replicating a service across machines.
When using the work-in-progress lxc provisioner, tsuru will behave like Mesos, but it's no that stable yet. First we worked on getting it working with EC2 instances, and now we are working on lxc and frontend integration.
That said, if you are looking for an open-source platform as a service, OpenShift, or as others mentioned, CloudFoundry are more mature options.