I must admit I am a little confused about how it works. It’s like a prettier, non-FOSS version of Jenkins that I can run in my cluster?
What do I get when I pay - a link to the source code that I can run? do you distribute an OVF?
Pretty much! Also because the tooling is hosted, you get updates and new features constantly with no effort required. If you have scripts to setup production environments, they can usually be tweaked pretty easily to create CI environments.
You install an agent (currently distributed as a ruby gem and a debian package) onto the server you want to run the tests on. And when new builds come in, they automatically get run on your server, and the results get reported back to Buildbox.